PCM Tuning Process Flow

1.DISABLE ALL TORQUE MANAGEMENT – This willeliminate all torque management within the PCM. Ignore this step for a standardtransmission (M6) and continue to step 2.
A. Open the VCM Editor>Edit>Transmission>TorqueManagement
B. Set Abuse Mode Enable = False
C. Set Abuse Mode RPM, Abuse ModeTPS and Abuse Mode Speed = 0
D. Select>Abuse Mode TorqueReduction vs. RPM. Set all values = 0

2.LTFT TUNING –
A. In the VCM Editor>Edit>EngineDiagnostics>General>MAF Sensor Fail Frequency = 0. This will set a P0103code and turn on the SES light. Ensure that the P0103 DTC is enabled and youare seeing P0103 in the DTC list. Don’t worry about the DTC at this time.

B. In the VCM Editor>Edit>Engine>SparkAdvance>Main Spark vs. Airflow vs. RPM Open Throttle/Moving. Copy the High Octanetable to the Low Octane table. The computer reverts to the low octane tablewhen a MAF failure is indicated, this will assure optimal timing.
C. Start the VCM scanner>Histogramdisplay. File>Connect. Then Tools>VCM Controls>Fuel & Spark>FuelTrim Learn>Reset Fuel Trims.
D. Changes to the LTFT’s do not take effect immediately – the PCM requires about50 minutes or roughly 100 miles to allow for the PCM to relearn the fuel curve.Try not to enter PE mode while driving and logging for this procedure. Logabout 30 minutes of driving at many different speeds and conditions. Try to hitas many cells in the histogram as possible. Stop logging and save the log. Do NOTturn off the engine until the log is saved or it will be lost. Go to VCMScanner>Histogram display>LTFT's. Open the VCM Editor>Edit>Engine>Airflow>MainVE and select Primary VE vs. RPM vs. MAP.
E. The goal is to get ALL LTFT’s between -5 and +5. Positive LTFT'sindicate fuel is being added because of a lean condition. Richen this cell byincreasing the VE table value by the amount of the LTFT value. The operation isopposite for negative LTFT's.
If LTFT = (4), VE cell value is 67, result would be (67)+(4)=71- increasing the VE, which is adding fuel. If the LTFT was (-4), the resultwould be (67)+(-4)=63, decreasing VE and thus reducingfuel. To decrease LTFT values, a smaller number or number closer to zero, ADD thedifference between the positive LTFT value and zero to the corresponding cellin the VCM Editor>Edit>Engine>Airflow>Main VE>Primary VE vs. RPMvs. MAP table. To increase a LTFT value, a larger number or number farther awayfrom zero, SUBTRACT the difference between the LTFT value and zero and SUBTRACTfrom the corresponding cell in the VCM Editor>Edit>Engine>Airflow>MainVE>Primary VE vs. RPM vs. MAP table. For example, In the VCM Scanner>Histogramdisplay, the (.8, 40) cell, 800 RPM's and 40 kPa, is 4. To bring the VCM Scanner>Histogramdisplay>LTFT cell (.8, 4.0) DOWN to 0 from 4 ADD 4 to the (.8, 4.0) cell inthe VCM Editor>Edit>Engine>Airflow>Main VE>Primary VE vs. RPM vs.MAP table. If the VCM Scanner>Histogram display>LTFT cell (2.0, 30) is-10, SUBTRACT 10 from the (2000, 30) cell in the VCM Editor>Edit>Engine>Airflow>MainVE>Primary VE vs. RPM vs. MAP table to bring it UP to 0. This will not workout exactly but will be VERY CLOSE.

F. Repeat steps D-F until ALL values in theVCM Scanner>Histogram display>LTFT are between -5 and +5. Try tocomplete this on the same day for best results as LTFT values can vary +-4% perday.
G. Once all values are between -5and +5, look at the VCM Editor>Edit>Engine>Airflow>MainVE>Primary VE vs. RPM vs. MAP>3D Surface graph. If the 3D Surface graphlooks choppy, click on polynomial smoothing ONCE. This will smooth out thetable values and provide a crisper throttle response. The table can also behand smoothed using the 3D graph. Look for spikes in the table andincrease/decrease the cells around the spike, creating a smooth table. Nowrescan, and go back to step E.

3.WOT PE TUNING – Do this only AFTERall LTFT's are -5 to +5. This methoduses the stock narrow band oxygen sensors which are not accurate for this typeof tuning.
A. Open the VCM scanner, do notworry about resetting the fuel trims they should be learned at this point. Ifnot, it takes roughly 100 miles or 50 minutes of driving to set the LTFT's.
B. Open the VCM Scanner>Histogramdisplay and do a nice 0-70 or preferable 0-100mph run. Look at knock retardFIRST. If knock retard is present, skip to section 4. If knock retard is notpresent, continue to the step C.
C. Open the VCM Scanner>Histogramdisplay>Air/Fuel tab and look at the 100(kPa) row.Most cars seem to like narrow band oxygen sensor reading between 890mv - 900mv.
D. For example, at 100(kPa), 3200(RPM) the narrow band oxygen sensors are at950mv. We want to bring that down to 890mv. Go to the VCM Editor Engine>Fuel>PowerEnrich, PE Enrichment>V8 Mult vs. RPM. Makesure Plus andSelected are bubbled in. In this casethe narrow band oxygen sensor is reading rich, so bring it down by SUBTRACTING.01. NOTICE THE DECIMAL!!!! VERY IMPORTANT!!! If lean, BELOW 890mv then ADD .01at a time. This is a small increment but we do not want to hurt the motor.
E. After making the changes, go backto step B and repeat until the oxygen sensors are in the 890mv to 900mv range.

4.ELIMINATING KNOCK RETARD -
A. In the VCM Scanner>Histogramdisplay>Retard, look for ANY knock retard. For example, cell (4.0, .20) shows4 degrees of knock retard. This should be 0, so SUBTRACT 4 from the VCM Editor>Edit>Engine>SparkAdvance>Main Spark vs. Airflow vs. RPM Open Throttle/Moving>High Octane (4000,.20) cell. Values cannot be less than zero in this table.

B. In the VCM Editor>Edit>Engine>SparkAdvance>Main Spark vs. Airflow vs. RPM Open Throttle/Moving>High Octane, goto the (4000, .20) cell AND/OR whatever other cells that have knock retard andSUBTRACT the amount of knock retard that is present in the Histogram display fromthe value that is in the corresponding cell in the VCMEditor>Edit>Engine>Spark Advance>Main Spark vs. Airflow vs. RPMOpen Throttle/Moving>High Octane table. Subtract by simply clicking on the Plus selection and in the box type -4 orwhatever number you have to subtract by and click commit.
C. Scan again and verify NO knock retardis present. If still present, repeat from step A.

5.A4 TRANSMISSION SETTINGS -
A. Ensure all Torque Management isdisabled. If not, see Section 1.
B. Open the VCMEditor>Edit>Transmission>A4 Shift Speed. Set WOT Shift Enable %TPS =90.
C. Set WOT Shift Disable %TPS = WOTShift Enable %TPS-10 or 80 if you used the parameter in step B.
D. Look at VCMEditor>Edit>Transmission>WOT Shift RPM vs. Shift. Set these tableparameters to the desired WOT shift RPM for each gear. Keep in mind there is aslight delay at the shift point that will cause the engine to exceed these RPMsettings. Ensure the VCM Editor>Edit>Engine>Fuel Control>FuelCutoff, DFCO>RPM Limits>P/N Cutoff RPM is roughly 500 RPM higher thanthese settings. We don’t want to hit the rev limiter during the WOT shift. Set Normal, Performance,and Hot tables to the same parameters.
E. VCMEditor>Edit>Transmission>WOT Shift Speed vs. Shift--PLEASE PROVIDE MEWITH A GOOD LINK FOR THIS. I KNOW THERE ARE TABLES/CALCULATORS PER GEAROUT THERE.
F. VCMEditor>Edit>Transmission>Shift Speed vs. %TPS vs. Shift = Leave stockparameters.
G. Go to VCMEditor>Edit>Transmission>A4 Shift Properties>Desired Shift Time vs.Torque>Normal. I basicallyguessed here, and could use some input. For the first half of
the torque band, I set shift time to .500 so you get nice soft, smoothshifts. Starting about midway, I decreased to .250 and for last 1/4 Ichanged to .100. I heard you do not want to go below .100 or else you willrun into some kind of gear crossing? Please feel free to fill in here.
H. Go to VCMEditor>Edit>Transmission>Base Shift Pressure vs. Torque vs. Gear. Okaythis is kind of weird and I don't understand it, but what I PERSONALLY did wasagain take half of the chart and to the left. Take this and set to a LOW# like 10. I have a shift kit in my car, and setting first half gives menice smooth shifts. You would never know I had a shift kit or torque converterin my car. I then took the middle and started beefing up shifts inincrements of 10 then increments of 15. By far right of table I haveshift pressure up to 96. Now, when you drive my car at 0-1/4 throttle itis SMOOTH. 1/2 throttle, you can feel a nice crisp shift. WOT it chirpstires from 1-2 and 2-3 shifts nice and hard.
I.Upshift/Downshift pressure modifiers - I don't understand. If you do, teach me and I'll update.
J. If you have a shift kit, leavemax line pressure at 90. If not you can probably set to 100.

The Basics

Other Important Values

IAC (idle): 30-50

IAC (load): <120

Injector Duty Cycle: See the chart below

Knock Retard: 0

LTFT’s: -5 to +5

MAF Flow:

Timing: 26-28 WOT, 15-18 idle

WOT 0₂: .880-.890 for narrow band sensors

Injector Duty Cycle Chart- The general rule is to not exceed80% duty cycle.

Fuel Trim Cell Info

Non load cells 0-5, 21
Idle 17-20
Part Throttle 6-14
WOT 15, 22

AFR Info

Here is achart that I have that should give you some insight into what standards are forlean cruise etc...
9.0:1 BLACK SMOKE (NO POWER)
11.5:1 RICH BEST TORQUE @ WOT
12.2:1 SAFE BEST POWER @ WOT
13.3:1 LEAN BEST TORQUE @ WOT
14.6:1 STOCHIMETRIC AFR ( CHEMICALLY CORRECT )
15.5:1 LEAN CRUISE
16.5:1 BEST FUEL ECONOMY
18.0:1 CARBURETED LEAN LIMIT
22.0:1 EFI LEAN LIMIT

PE Tuning Info

NaturallyAspirated

Air/fuel ratio for peak poweris 12.8. If tuning on a Dynojet, try for 12.2 – 12.5air/fuel ratio. If tuning on a Mustang dyno or on the street try for 12.8 –12.9. Some tuners say that LS motors run the best at 13.1. The AFR curve shouldberich up to max torque then lean out slightly up to maximum RPM and then go alittle rich a few hundred RPM’s beyond maximum forsafety.

PE Delay

If the RPM is below the delay RPM definedit will blend in PE at the PE enrichment rate. That’s why many people set theenrichment rate to 1. With a lower RPM delay PE will apply immediately abovethe RPM specified and full PE will activate at the RPM specified.
Normal practice for automatic transmissions is to set that RPM limit to thestall speed of the converter. For manual transmissions set it a little lessthan the take-off RPM. An enrichment rate of 1 effectively negates thedelay RPM. For cars that experience tip-in knock retard at WOT this isoften the solution.

VE Tuning Info

HigherVE values add fuel (telling thePCM you have more useable oxygen in the cylinder)

Lower VE values subtract fuel (telling the PCMyou have less useable oxygen in the cylinder)

If using a MAF sensor, only tune the idleand part throttle areas of the VE table, 4000rpm and below. If not using a MAF (SpeedDensity), tune the entire operating area of the table.

A rough VE table will be more susceptibleto burst knock retard.

1. I personally smooth eachtime, but I don't think it's necessary. I don't stick with the raw polynomialresults, however. I have a spreadsheet which compares the poly value to therange the value should be within to stay within my AFR range. I don't let the valuefall outside of these bounds.

3. The adjoining cellsshould be smooth not spikey.If it's a dip, it should look like a U, not a V. You should tweak the spike andthe values around it to smooth it out.

4. I'm guessing that themax VE cell value you'll see for a stock vehicle would be ~100-110. I thinkI've seen VE tables from FI cars which are in the 150+ range.

itskinda like this. from the factorythe ve table is the backup controller, the maf is the primary measuring device for airflow, the maf reading is double checked against the ve table to make sure nobodies gone crazy. Now in a perfectworld you VE table would be perfectly tuned to match your engine then you plugthe MAF in and perfectly tune it to match your VE table.
Now for the imperfect world most of us live in.
Log your rpm, mass air flow g/sec (use imperial pounds if you must), mass airflow frequecny, TP, dynamic cylinder air and fueltrims, save the logs
Now what you will have to do is open the log in excel and figure out what frequencyareas of the maf need massaging to bring your fueltrims in line, keep in mind that changing the VE alone will not make much ifany change to the fuel trim but changing the MAF flow VS frequency even 1%makes big changes. Also keep in mind that if you change mafwithout changing VE you can start setting codes and getting flat spots and bogsin throttle response.
confused yet?
Its not that hard, histogram shows which VE cell, ifyou look at raw data in excel you will easily find the MAF frequency that wasin play when that particular cell was in use. My rule of thumb is if I add 1%to a MAF frequency range I will add double (2% in this example) in the VE cellsin that range.

VE and Burst Knock

Once the VE table is correct, tune outany detected burst knock by increasing the Edit>Engine>SparkRetard>Burst KR Enable Delta Cyl Air Threshold vs.RPM table. The ultimate measure is whatever it takes to eliminate the errorbetween commanded and measured AFR.

SD Tuning, LTFT’s and MAF Table Scaling

Oncethe MAFless (SD) VE table is correct and the mass airflow sensor is reconnected, the LTFT’s will gopositive. Nowscale the VCMEditor>Edit>Engine>Airflow>MAF Calibration>MAF Airflow vs.Output Frequency table positive to get the LTFT’sback to where they were when it was MAFless (SD). Thepoint is to get an accurate VE table and then adjust the MAF calibration tableto agree with the VE table at the observed LTFT values.

MAF Sensor Info

Thestock mass air flow calibration is correct +-4% as long as nothing in theintake tract has been modified. If the MAF meter, air lid, air intake, or airfilter has been modified than the MAF Airflow vs. Frequency table will needmodification. Do this after the VE table has been corrected.

MAF Tuning – In Work

1.)Make sure you log Dynamic Airflow vs MAF Frequency(Hz) In HP Tuners it is measured in lb/min so we will have to convert thislater for the MAF table (g/sec).
2.) Go do enough driving to log a variety of MAF frequencies. You probablywon't get a whole lot of data above 10,000 Hz or below 2000 Hz, but get as muchas you can. Cruising on the highway is a good place for this as you can coverall rpms and a wide range of mph.
3.) Save the log run and export the data into an Excel readable format and sortthe data by MAF frequency (smallest to largest).
4.) Section off MAF frequency ranges that register with the frequency points onthe MAF table (i.e. For MAF table freq = 3000, you want to use the data youlogged in the range of 2940 to 3065) Take the average of all the DynamicAirflow data in this range. The reason you want to use this range is so thatthe average is calculated using a sort of 'swing error' thatstraddles the calibration point itself.
5.) Once you have calculated averages for each range (this will be very tediousand take quite a bit of time, but using excel functions makes it much easier)you will have new MAF Airflow data to rebuild the table with. 1 lb/min is equalto 7.58 g/sec so do that calculation and you will derive a new MAF table.
6.) For all the calibration points that you were missing data for (above 10KHz, below 2K Hz) you can either shoot in the dark and scale up accordingly, orif you choose to log raw MAF air readings in tandem with Dynamic Airflow andfrequency, you can calculate the variance b/w your dynamic airflow and MAFairflow and scale up by the trends you see on either extreme. (i.e. If as youget closer to 10K and you notice the dyn airflow is10% higher than the stock MAF airflow, then you can go ahead and'assume' that above 10K Hz it will most likely behave the same,otherwise you could try to log 155+ mph runs)
I know this seems like a very painstaking way to do this but it worked verywell for me and using a lot of excel functions I was able to reduce the time onthis project significantly. I have verified that my MAF reports almost exactlywhat dynamic airflow the motor sees and therefore does not cause any confusionfor the trims (this other bit of business in this thread is not MAF related).Some people have tried using scatter plot functions to derive equations thatwill supersede any manual calculation, but having to 'best fit' thecurve for the logged data leaves an element for bias and human error. Manualcalculation appears to be the most error free method that I can think of.Hopefully someone can come up with an easier way!

LS1 VCM Main Airmass Calculation

The VE table looks as though it is inmeters cubed; it is just not used like a conventional VE table. The VE valuesare such that the PCM can directly back calculate to g/cyl,the primary means to determine fueling and timing.
This is what makes it so confusing. You can't solve for air mass, you have tosolve for g/cyl.

The equation
VE = ((mass flow * IAT / (MAP * RPM * Displacement))
Mass flow: grams/sec
IAT: Degrees Kelvin
MAP: Bar
RPM: RPM
Displacement: Cubic Meters
To solve for the mass flow in g/sec simply re-arrange the equation.
Mass flow = (VE * MAP * RPM * Displacement) / IAT

A very important calculation the VCM must make to ensure correct fuel mixturesunder all driving conditions is the dynamic air mass calculation. This is themain calculation the VCM uses to determine how much air it should use for theBase Fuel Calculation (Inj PW). The air masscalculation is not simple and uses various combo's of MAF and SD inputsdepending on engine operating conditions such as current engine RPM. It mayalso make decisions based on whether the engine is in a steady load state(steady MAP) or unsteady load state (Unsteady MAP). Note, that these thresholdschange with RPM and MAP. E.g. at higher RPM or high MAP readings you have moreleeway before the VCM decides that you have an Unsteady MAP condition. Thisunsteady MAP definition is basically there to decide if a throttle transienthas occurred (or other) i.e. the MAF input is known not to be accurate underthese operating conditions.
Under normal conditions (i.e. all sensors working properly) in the code I’mlooking at it is like this:
(caveat: many of these thresholds may vary between code revs and vehicle type)
RPM > 4000
----------
trust MAF completely and ignore SD calcs(apart from MAF sanity checking purposes)
RPM < 4000
----------
if RPM < 2400 and MAP < 84 kPa then
Steady MAP threshold = 0.0 kPa
else
Steady MAP threshold = 0.8 kPa
If (Steady MAP) then
Calculate MAF Air mass/SD Air mass ratio (used forUnsteady MAP operation)
Correction Air mass = MAF Air mass (filtered)
else
Correction Air mass = SD Air mass x MAF/SD Air massRatio (calculated during Steady MAP conditions)
Transient Corrected Air mass = previous Final Air mass + proportionof Correction Air mass
Final Air mass = fn(MAF Airflow, previous MAF Airflow, prev 3 MAP readings, prev 3 TPSreadings,
Transient Corrected Air mass)
There are 9 coefficients to this filter (and a total of up to 16different sets of coefficients depending on operating conditions). It is worthnoting that the previous value is weighted heaviest followed by the 2 MAFterms, so MAF dominates IMHO).
There are also a number of checks at the end to make sure things donot exceed certain limits.
To summarize:
1. High RPM behavior is totally based on MAF
2. Mid RPM behavior has an allowance on Steady MAP behavior before it switchesto Unsteady MAP
3. Low RPM behavior (where the bulk of the fuel cells are) is dictated byunsteady MAP behavior that is still mostly dominated by the MAF input withsmall tweaking from SD)
If the VCM decides that a throttle transient has occurred (unsteady MAP), theairflow incorporates a 'correction' from the SD calculations. Thisvalue is the SD calculated air mass multiplied by the previous ratio ofmeasured MAF air mass to calculated SD air mass (this normalizes it, since youare worried about the transient deviation from MAF air mass only). The way Iunderstand it is this, imagine you are cruising (MAP is steady), you have adecent vacuum in the manifold and you change the throttle position quickly. Airrushes into the manifold to service the change in air demands from the engineitself but also to try and fill the vacuum. The result is that the MAF readshigher than it should at that point in time (spikes). This is more pronouncedat low RPM where the engine airflow is smaller and the relative proportion of extraairflow due to filling vacuum is higher, also the MAF is known to be moreinaccurate at lower RPM and more non uniform airflow. IMHO, the SD correctionis to account for filling and emptying of the manifold during throttletransients and also to smooth the MAF's spikiness atlower RPM’s.
The bottom line is that if the engine is at a steady load state or operating athigh RPM then the airflow is 100% based on the MAF once you get thru all thefilters and calculations. And the SD calcs only getused for transients and smoothing lower speed operation.
At no stage does the MAF get ignored completely in these calcs(the dominating terms of the main filter calc are always MAF based).
An interesting point to note is that removing the MAF basically bypasses thewhole system and directly sets the Final Air mass value to be the result of theSD lookup (it also disables things like knock learn and a few other nicethings). Most have taken to calling this 'Backup SD Mode' which is asgood a name as any I guess and I meant to allow the engine to run with a failedMAF (although it is quite possible to tune using this mode (e.g. HSV GTS 300kwcomes factory this way). There is another way to disable the MAF systemcompletely (i.e. without setting the DTC's) and bytuning of the thresholds and other flags you can get a fully functional SD tunehappening, the so called 'True Speed Density Mode'.

LTFT and STFT Info

STFT Info

The PCM uses the Short Term Fuel Trim(STFT) for real time fueling corrections. They have a 10% window that will onlyaffect the Long Term Fuel Trim (LTFT) if the fueling correction is beyond the10% window for 10 seconds. If this condition exists, the LTFT is changed andacted upon during the next PCM timed cycle, which is every 10 minutes.

LTFT Info
Thepurpose of LTFT’s is to compensate for engine andsensor age and variation over time.

+LTRIMS, PCM is sensing a lean condition and adding extra fuel

- LTRIMS,PCM is sensing a rich condition and subtracting fuel

Positive long term fuel trims(LTFT's) indicate the PCM is commanding more fuel inorder to compensate for what is being perceived as a lean condition. By doingso it maintains a stoichiometric air-fuel ratio of 14.7:1 during closed loopoperation. That is, less than wide open throttle.
Negative LTFT's indicate the PCM is commanding lessfuel due to what is perceived as a rich condition although the air-fuel ratioremains the same at 14.7:1 and in reality it's neither truly lean nor rich.
However, positive LTFT's can result in a rich air-fuelratio during WOT operation because the PCM will add fuel in addition to the PEtable. If they were negative no fuel is subtracted during WOT as that couldresult in a lean condition resulting in detonation.
If the LTFT's are positive, often resulting in a richAFR during WOT, horsepower may be gained by getting the LTFT'sas close to zero or slightly negative during closed loop. In this way noadditional fuel is added during WOT. If the LTFT'sare negative no additional horsepower can be gained because the AFR at WOT isthen determined solely by the power enrichment table without any additionalfuel being added except during CAT over temp conditions.

To put it simply what'shappening is the Mass Airflow Sensor (MAF) is calibrated to expect outside airtemperatures and temperature change rates within a specified range. When youadd an aftermarket intake you often get colder and therefore denser, moreoxygen rich air, than what the MAF is calibrated for. It interprets this asmore air than expected when in reality there really isn't. In turn the PCMtells the injectors to stay open for a longer period of time by lengthening theInjector Pulse Width in order to inject more fuel into the combustion chambers.By doing so the air-fuel ratio remains at 14.7 parts of air for every one partfuel. Hence it is neither lean nor rich but rather right where it's supposed tobe.
But, when you go WOT the PCM remembers it had to add additional fuel duringclosed loop and adds this extra fuel in addition to a predetermined amountcalled for in the Power Enrichment vs. RPM table. This results in a too richcondition at WOT and a loss of horsepower. Or to put it another way: not asmuch H.P. as you can obtain should that extra fuel not have been added.
For this reason you want the LTFT's as close to zeroor slightly negative during closed loop so no extra fuel is added during WOT.You do this by using scanning software and a program such as LS1 Edit, etc. toget the LTFT's correct. Once they are you can thentune WOT using a wideband O2 meter and typically adjust the PE vs. RPM tablefor the AFR you want. Note: some applications such as nitrous or forcedinduction cars usually require a richer AFR than a normally aspirated car.
What is closed loop you ask? Closed loop operation means the front O2 sensors(forward of the catalytic converters) are used to help determine the AFR andoffer feedback to the PCM as to the current AFR. The PCM then adjusts theinjector pulse rate to maintain a 14.7:1 AFR. So it's just that, a closedfeedback loop.
What does open loop operation mean? Well, instead of using a closed feedbackloop (the O2 sensors are not used for input) the PCM uses a lookup table that,to put it simply, is just a table that says 'at this RPM use X amount offuel.' This is called the PE vs. RPM table or 'Power Enrichment vs.RPM' table.

Deleting Rear OxygenSensor’s

Driver Side Codes:
137 - HO2S Circuit Low Voltage Bank 1 Sensor 2
138 - HO2S Circuit High Voltage Bank 1 Sensor 2
140 - HO2S Circuit Insufficient Activity Bank 1 Sensor 2
141 - HO2S Heater Performance Bank 1 Sensor 2
Passenger Side Codes:
157 - HO2S Circuit Low Voltage Bank 2 Sensor 2
158 - HO2S Circuit High Voltage Bank 2 Sensor 2
160 - HO2S Circuit Insufficient Activity Bank 2 Sensor 2
161 - HO2S Heater Performance Bank 2 Sensor 2

Go to Edit>Engine Diagnostic’s>DTC’s>Error Mode= 3 for each of the codes above.

Go to Edit>Engine Diagnostic’s>DTC’s>SES Enabled = Off foreach of the codes above.

Idle Info

General Operation
The PCM calculates the IAC position based on a number of Airflow calculationsand estimations, the final idle airflow value consists of the following twomain components:
- Base Idle Airflow (Base +LTIT)
- Adaptive Airflow correction(STIT)
LTIT = Long Term Idle Trim
STIT = Short Term Idle Trim
Note: These names are made up to moreeasily understand than proportional, integrator, slow filtered idle airflow, etc.

The first thing to realize is that the PCM only runs the adaptive idle controlroutines when at idle conditions (below certain TPS and MPH limits). However,the base airflow routine is controlling the IAC position during all drivingconditions (things you are aware of already, such as the Throttle Cracker, andif you set your Base Running Airflow values too high you get cruise controletc.). The combination of all these components is what I call the Base IdleAirflow in grams/sec.
Base Idle Airflow
The Base Idle Airflow is combination of looked up values from various tableswithin the PCM and also incorporates a Long Term Idle Trim (LTIT) correction.This airflow directly controls the IAC position when at non-idle and is the'starting point' for adaptive idle control. The base airflow consistsof the sum of the following individual components:
Base Running Airflow
- this is the main Idle Airflow when in PN (A4 only) or Gear (A4 or M6)
- a table vs ECT
Startup Airflow
- additional airflow during engine startup and initial run period (decays tozero in the first few seconds of engine operation)
- a table and a few delays and decay rates
Startup Spark Retard Airflow
- airflow correction to account for startup spark retard (if used)
Fans On Airflow
- Additional airflow to account for increased engine load during cooling fanoperation
- Two values depending if one fan active or both active.
DFCO Airflow
- used to set IAC position during DFCO
Throttle Cracker Airflow
- additional airflow to open the IAC based on MPH and RPM
- zero during idle conditions
- a table
Throttle Follower Airflow
- controls rate of closing the IAC valve during throttle closure
- zero during idle conditions
- a few tables of initial value and decay rates
Long Term Idle Trim Airflow (LTIT)
- a slow moving correction based on the adaptive idle routines (think LTFT's for fuel)
- the idea of this correction is to bring the Short Term Idle Trims (STIT) tozero
- it has +ve and -ve limits
- a calculated value
AC Airflow
- airflow correction for when the AC is on, this is a torque based calculationthat estimates how much torque the AC is pulling and calculates an airflowcorrection to compensate.
IAC Park Airflow
- airflow used to calculate IAC position when ignition is off and engine notrunning
- used in place of all of the above
- a table
Adaptive Idle Control
The whole point of the idle control routines is to maintain the desired IdleRPM. The PCM therefore needs to 'close the loop' and use the Idle RPMerror as a feedback to provide this control. The monitoring of the Idle RPMresults in a Short Term Idle Trim (STIT) that provides the fast moving closedloop control of the IAC valve. Again here it is very analogous to the STFT's and feedback from the O2 sensors. That’s why I chosethese names rather than Proportional, Integral, and Derivate.

Okay, so the PCM has a Desired Idle RPM it is trying to achieveand it is constantly measuring the current RPM and calculating an Idle RPMerror value. The PCM uses various aggressive and not so aggressive algorithmsto control the STIT, to provide fast convergence (and also stall savercapability) but also reasonable idle stability.
During all this, the PCM ismaintaining a fairly complex state machine of, Are we at idle?,Is the engine transitioning back to idle?, etc. The PCM does remember a fewdifferent last known state of the STIT, for example,when you turn on the AC the PCM stops updating the 'ACoffSTIT' and starts updating the 'AConSTIT' (again here think Fuel Trim cells). The idea of this is that whenyou turn the AC off the PCM can quickly return to the original IAC operatingpoint. For A4 vehicles you also have the PN/Gear dimension as well.
A good example of the STIT inaction is if you have an M6, you have your foot on the brake and you partiallylet the clutch out and you feel the engine pull harder to try and maintain thedesired idle RPM. If you were logging the IAC steps or the desired idle airflowyou would see it increase. Monitoring the LTIT and STIT is a very good tool toget your Base Running Airflow values correct, ensuring your LTITsare not maxing out on the limits and troubleshooting PN/Gear and Fan On/Offstumble etc., especially after head/cam install.
Desired Idle Airflow
The net result is that the PCM takes the Base Idle Airflow (including LTIT) andthen adds the STIT to come up with a final Desired Idle Airflow (whichgenerally is available as a PID for logging). Then there is a final step thattakes this airflow value and translates it to the actual IAC valve position orthe ETC TPS position. It's basically just a unit’s transformation for the mostpart and the IAC and the ETC have their own control routines and state machinesthat effectively take this idle airflow as an input.
The 'Desired Idle airflowpart, which is the final 'airflow' value the idle control routinesdeliver to set either the IAC motor position or the ETC position.
After the 'Desired IdleAirflow' is calculated, it is then translated into an 'Effectivearea' value in square millimeters (mm²). This is the crosssectional area required to deliver the airflow desired (taking into account airdensity and pressure ratio across the throttle/IAC). Now at this point thecalculation branches to either IAC or ETC.
If IAC is installed the'Effective Area' is translated into a number of 'steps'that delivers this area (a table of IAC Steps vs. Effective Area).
If ETC is installed then thereis a single value that translates 'Effective Area' into 'Desiredthrottle area percent' units of % area per mm². This number isthen handed over to the ETC routines that control the ETC TPS %.

The ETC logic is quite simple in that it has two maininputs the Accelerator Pedal Position (APP%) and the'Desired throttle area percent' (IAC%). In the ETC code there is amaximum value that the IAC% is clipped at as a safety check (mostly on thethrottle cracker), but the Throttle Cracker, Follower, Adaptive and variouscompensation routines are all the same tables (i.e. the ETC code has nothingextra).
Now, the ETC looks at the APP%and checks if it is 0. If it is not 0 then the commanded ETC position is adirect function of the APP%+IAC% (accounting for throttle cracker). If it iszero then the ETC position is controlled via the IAC% (as you would expect).
Once this ETCDesiredThrottleArea%has been passed thru the numerous limiter functions (ETC RPMlimiters,MPH limiter, TorqueMangement etc.) the final ETCRotation% is calculated via a simple transfer function of ETC Rotation% vsDesiredThrottleArea%.
There are maximum slew rates,minimum position checks and a few other parameters here, but in terms of idlenothing else comes into it.
Unless you have modified yourETC in anyway, there would be no reason to change the ETC% vsEffectiveAreascaler oranything else there as far as i can see.

What else?
In addition to the Idle Airflow routines the PCM also has an RPM based idlespark correction 'closed loop' operation that it uses to control theidle RPM. Since the spark advance can move much faster than the IAC, it canprovide very fine control of idle speed. When logging you will see this as ajagged spark advance chart, most noticeable with cams at lower idle RPM’s where the spark advance generally oscillates between itsmin/max allowed values as the engine lopes at idle.

Idle Tuning

To set idle speed go to VCMEditor>Edit>Engine>Idle>Idle RPM>Target Idle RPM vs. ECT tableand change cell values to desired idle RPM. If idle RPM is modified up or down,the VCM Editor>Edit>Engine>Idle>Base Running Airflow>IdleAirflow vs. ECT table must be adjusted up or down also.

If a lean idle condition ispresent modifying VCM Editor>Edit>Engine>Fuel Control>Open &Closed Loop>Idle Proportional Fuel Tables = Offwill most likely eliminate it and any low RPM surging.

A Basic Idle Tuning Strategy

1. Set idle speed to desired RPM. 900-950 is good for cars with aftermarket cams.
2. Go to all your spark tables and set the park and drive idle values to about 22 degrees.
3. Now switch to a scanner that lets you see IAC counts and TPS voltage. This is where we will spend some time.
4. We want IAC counts to be 40-60 for cars with aftermarket cams. The stock cam runs about 60-80 counts. A car with an aftermarket cam will want less IAC counts.
5. To reduce IAC counts turn off the car. Turn the idle set screw clockwise to open the throttle blade a LITTLE. Unplug the TPS, turn the key to the on position, DO NOT start the car, for 30 seconds. Turn the key off and plug TPS back in.
6. Start the car and begin scanning. Monitor the IAC counts and repeat step 5 until the IAC counts come into line. It will take about 4-6 times to get the IAC counts correct.

Note:Keep in mind that TPS voltage must be in the .4 to .6 range. If above or belowthis voltage, the PCM will fall into the wrong cell at idle. Check the TPSvoltage each time the set screw is adjusted and adjust as necessary.

Another adjustment that will help start-upand idle is to go to the cranking VE table and multiply the whole table byabout 80% to lower it. Now go to the primary or secondary, if the PCM has it, VEtable and drop about 3-6 counts off the idle area.

Open Loop Idle Fueling

The VCMEditor>Edit>Engine>Idle>Base Running Airflow>Idle Airflow vs.ECT table is like a software choke that is used to control the mixture at idlewhen the engine is in open loop. It controls AFR by opening or closing thethrottle blade slightly to meet the values in the cells at a given coolant temperature.

Closed Loop IdleFueling

For closed loop idle fuelingthe 400, 800, and 1200 rpm cells at the lowest MAP value’s in the VCMEditor>Edit>Engine>Airflow>Main VE>Primary VE vs. RPM vs. MAPtable has control over idle fueling.

Tuning the VE table in HPTuners - Overview

Wideband and Narrowband methods
The LTFT value is your indicator of how much error is in your VolumetricEfficiency table. If Block Learn is at 0% everything is just right. If yourSTFT is more than 3 % away from 0 , the LTFT value isstill 'learning'. A motor is considered well tuned to have LTFTvalues between +- 4%. Not every motor can achieve this though.

Stepby Step for SD tuning Wideband Method:
1: Unplug MAF sensor
2: Disable the SES lights for MAF codes P0101, P0102, P0103 (No check enginelight.) Do not completely disable the codes or the PCM will not fall into SDmode. Only turn off the SES light, DO NOT DISABLE THE CODES THEMSELVES!
3: Change all points to 1.13 in the Open Loop F/A vsECT vs MAP table (commands AFR of 13.0)
4: Change all points in the Closed Loop Enable Coolant Temp vsIAT table to 250* (Disables closed loop)
5: Copy High Octane table to the Low Octane Table (computer reverts to lowoctane table when MAF is unplugged, this assure’soptimal timing)
6: Change all points in the Power Enrich Fuel Multiplier vsRPM table to 1.0 (disables PE mode)
7: Use your wideband and HPT histogram to verify AFR of 13.0
8: Make adjustments to the VE table accordingly to dial in a 13.0 AFR using thedesired formula - current afr/13.0 = VE multiplier
example: cell @ 1600 rpm Map 50 is showing the air/fuel to be at 11.7 in the histogram. 11.7/13.0=0.9 Lets say that your VEtable has a value of 48 listed at 1600 rpm, Map 50. Using the above formula youwould multiply that value times (.9). 48*.9=43.2. 43.2 would be your new VEvalue. Continue using this formula until all data has been plotted.
9: Hand smooth VE as described by Magnus (a smooth VE results in crisperthrottle response), upload new .bin and repeat steps 7 and 8 until all cells inthe histogram are 12.8 - 13.2.
10: Change all points in Open Loop F/A vs ECT vs MAP table back to stock (re-enable stoichcommanded AFR)
11: Change all points in the Closed Loop Enable Coolant Temp vs IAT table back to stock (re-enables closed loopoperation and fuel trim leaning)
12: Change all points in the Power Enrich Fuel Multiplier vs. RPM table back tostock (re-enables PE mode)
13: Use wideband and PE table to dial in desired WOT AFR. (Optimum HP at WOT)
Step by Step for SD tuning Narrowband(stock) o2' Method:
1st a couple of things to keep in mind:
a: This method will not be as accurate as the one above, but it should get youreal close for part throttle.
b: Please keep in mind that depending on where youhave your PE enable settings, you will probably only get '0' LTFT values in your histogram after 4,000 RPM.
c: For WOT you will still need a WBo2.
d: There will always be a 2-4% change in learning fromday to day. Weather, fuel, and engine dynamics vary quite a bit. It’s the VCM's job to learn these corrections. It is recommendedthat all tuning sessions be done in like weather conditions.
e: There are two methods of using the LTFT's tocorrect the VE table, below is a description of the two taken from the HPTuners help file. I will try to elaborate a littlemore on them.
1: Unplug MAF (Replace with strait bellows if you do not have intentions ofever using a MAF again ie. always speed density.)
2: Disable the SES lights for MAF codes P0101, P0102, P0103 (No check enginelight.) Do not completely disable the codes or the PCM will not fall into SDmode. Only turn off the SES light, DO NOT DISABLE THE CODES THEMSELVES!
3: Copy High Octane table to the Low Octane Table (computer reverts to lowoctane table when MAF is unplugged, this assure optimal timing)
4:Write your file to the VCM and go for a drive approx 20-30 minutes, and tryand hit has many cells as possible. Use the 'default' config file andscan your LTFT's and STFT'sinto the histogram.
5: After you have logged sufficient data, it is now time to look at whatchanges you need to make. This will require looking at both the LTFT and STFTdata on a cell by cell basis.
a: If the majority of your LTFT cells, are greaterthan a 10% swing (+- 10), then refer to method 1.
b: If the majority of your LTFT cells, fall between+-10% then refer to method 2.
Method1 using the LTFT and STFT corrections from the scanner histogram data:
The VE table corrections can be derived by the following formula:
(+-LTFT%) + (+-STFT%) = Final % Learned
If your LTFT histogram value @1600 RPM, 30 kPa Map is+7 and the associated STFT value is -2 your total % fuel correction is +5. Useabout ½ the correction (2.5%) on the VE table cell @1600 RPM 30 kPa Map to avoid overshoot.
Repeat this process for any LTFT histogram value until you see a +- 4%range. After you reflash your VCM with the new VE table, use the VCMControls function to reset the fuel trims before you start recording newdata. This will give you a “clean slate” to work with.
It will take you the better part of an afternoon to log the LTFT, make thecorrections to the VE table, then verify the results on the histogram again.
Method2 using the STFT corrections only from the scanner histogram data:
This will require you to disable the LTFT process.
Use of this method requires your VE table to be no more than 10% off. If yourVE table is beyond this, start with method 1 first.
Depending on your model you can either turn the LTFT enable option to “Off”(Edit>Engine>Fuel Control>Open &Closed Loop>Long Term Fuel TrimEnable = OFF) or set the LTFT minimum Engine Coolant Temp (ECT) to itsmaximum value. Using the scanner reset your Fuel Trims. Go for a driveand record the STFT's.
The above step of disabling the LTFT learning process will let the VCM run theSTFT correction, but no make any LTFT corrections.
The advantage to this is you only have to use the STFT table on the histogramto get your fuel % correction values. You no longer have to do the(+-LTFT %) + (+-STFT %) math or keep track of the LTFT cell number in use.
The number derived in the histogram can now be used as a 1:1 ratio in the VEtable. So, if you are showing -7 in your histogram, you could subtract 7from the corresponding VE cell, the net result should be a value closer to0 during your next logging session.
This will take you about ½ the time to log the STFT, make the corrections tothe VE table, then verify the results on the histogram again.
Once you have achieved a histogram of near 0 values, you can go back into theeditor and re-enable your trims.

LS1Tuning Guide

This document will attempt to layout astep by step process to guide you in the tuning of your ls1 powered vehicle

Requirements

In order to properly tune your car thereare a few items that you need to have available

1. HP Tuners

2. Laptop computer

Outline

There are many different ways one cantune a car, but below I have outlined a methodical process which should workwell.

1: Set absolute parameters

2: Start car, verify

3: Tune idle

4: Tune part throttle

5: Tune WOT

1: Absoluteparameters

At this point the laptop is connected to thecar and the base program is downloaded and saved (*always* start with YOUR baseprogram). The number one thing to remember when editing the PCM is to make onlyone or a few small changes at a time.

First start with the'absolute' parameters. These values can be known and set withtotal objectivity. These generally include gear ratio, fan turn on temps, revlimiter, etc. Choose a desired idle rpm and enter it initially. The main ideahere is to keep the program as stock as possible - we only want to changevalues that have a concrete value - leave shift points, fuel, spark, and othersubjective values alone.

The only tricky parameter to set herewill be injector constant. This is because the LS1 does not have a manifoldvacuum regulated fuel pressure, so as manifold vacuum changes (and railpressure stays constant) the pressure drop across the injector change, so theinjector flow/constant itself changes. If a vacuum referenced regulator isused, (some supercharger setups, etc.) then simply fill in a constant valueacross the range.

2: Start car,verify

Now we will start the car and verify thateverything is working properly. Before we actually key on we should have ourscanning/logging software hooked up and ready to go. The suggested minimumparameters to be logged are:

RPM, MAF flow (g/sec or lb/min), MAFFrequency, MAP, Spark Advance, Knock Retard, Injector Pulse width (left andright banks), O2 sensors - B1S1 and B2S1, IAC Position, L-trim (left andright), S-trim (left and right).

In addition to any parameters of specialinterest, all data should be logged to disk.

Now we are ready to start the car. Startit and begin logging. First verify everything seems mechanically sound (oilpressure, etc.). Next, look at the MAF flow and/or frequency. As you blip thethrottle this value should increase/change. Let the car run for a while to heatup and go through its DTC tests. Watch out for any kind of SES light. If anyare observed determine if it is a mechanical/electrical problem or if it issimply caused by a new engine combination (camshaft, etc.). Once the vehicle isup to operating temperature verify that the O2 sensors are responding tochanges in the throttle. If the vehicle seems to be running decently (nopinging or potentially problematic situations) drive it around for awhile.Monitor the STFT’s, LTFT’s,and O2 values and ensure no great splits exist, exhaust leaks, etc. If the O2sensors are old or just aren't switching fast enough (anti-freeze and RTV canboth kill them easily) they should be replaced before continuing any further.

3: Idle

Now that we have verified everything isin proper working order we can begin tuning. Idle is the best place to start. Previouslywe set the desired idle rpm - subjectively decide if this rpm correct. If not,change the value and re-evaluate. Once the desired idle rpm is achieved, we canbegin tweaking it for stability. Take note of the IAC counts. In a no loadsituation (neutral, no ac) they should be no lower than 30, and no higher than50. A hole may need to be drilled in the throttle body or enlarge the one thatis already there to bring down the IAC values. Do this until they areacceptable. Now put a load on the car (D if automatic, and put the AC on). Thevalues here should be no higher than 120 or so. If they are enlarge the hole.

Repeat the above process until the IACvalues fall inline. If the idle is still unacceptable then try adjusting thetiming. Be careful of adding to much timing - it can give a great no load idle,but with any kind of load will become erratic. A 'hunting'idle is a sure sign of too much timing. To adjust the timing at idle the basespark tables are the easiest place. The tables are scaled vs. rpm and g/cyl of airflow. The rpm part is evident. To calculate theg/cyluse the followingformula:

g/cyl = 15 * MAF(g/sec) / RPM

This formula takes mass flow per unittime and converts it to mass flow per cylinder. The 15 is a constant whichcorresponds to the characteristics of a V8 running a 4-cycle combustion cycle.The easiest thing to do is to load the log file into excel (export it as aCSV), then create a formula in excel which applies the formula above.

4: Part Throttle

Not that the idle is correct and we haveverified that the car is in proper working order we can begin part throttletuning. The first step in this is to record a long log file of driving, aminimum of 20 minutes, but the longer the better.

Once we have a log file we can begin thedata reduction. The first element we will tune will be the fuel delivery. Atpart throttle the computer uses the MAF meter to find the amount of airentering the engine. It then calculates the amount of fuel required to maintaina 14.7:1 A/F ratio. It injects this fuel by controlling the injector pulsewidth. The O2 sensors, which are very accurate at 14.7:1, provide feedback tothe computer and let it know how close it is to the goal. The computer usesthis feedback to tweak the fueling of the motor to achieve a proper 14.7:1 a/fratio. This 'tweaking' is exhibited to through the STFT and LTFT parameters.These values indicate how the computer is correcting. Since injector flow andpulse width are known with great precision, and we have no control over theinternal algorithms we will assume that any inaccuracy (which is exhibited bynonzero trim percentages) is a result of an incorrect MAF transfer function.

In tuning part throttle we will tweak theMAF transfer function according to the LTFT values we logged. There are 2 waysof doing this, the simplest is to view the LTFT values, average them, and scalethe entire MAF table by a percentage which will give the LTFT’sa 0 to -4. LTFT’s are in units of percent so this iseasy. If the average LTFT’s are around +5 and we wantto shoot for -4, then we would just multiply the entire table by 109% (or anincrease of (+5 - (-4))=9 percent). Likewise if we were at -10 and wanted toshoot for negative 4 we would decrease the entire table by 6 percent, ormultiply by 94%.

Once this is complete repeatthe logging process above and check the new LTFT value. We want to avoidpositive LTFT values since they will be applied at WOT and will lead to inconsistentfueling. Negative values are okay, though we shouldn't go too far out of whack.

The second option is a little morecomplicated. It uses the same premise above, but instead of taking the averagevalue it applies a localized LTFT correction to each point of the MAF transferfunction and derives a new curve. This method is not for everyone, but incertain instances is very useful.

After repeating the above method until LTFT’s fall in line, fueling should be complete. Now we canaddress spark. Spark advance is a rather difficult item to tune directly, but hereis a suggested method. This method relies on a properly functioning knocksensor without any desensitization.

Assuming the car is naturally aspiratedand does not ping with the stock timing advance: Take the entire timing tableand increase it by 5 degrees. Now start driving the car while logging. Try andemulate every possible driving condition. If pinging is detected at any pointback out. If the car pings constantly reduce timing across the board twodegrees.

When done logging export the data to aCSV file and open in it excel. Here we will make a pivot table. Create a columnwith g/cyl, spark retard, and rpm. Use these threeitems to make a pivot table. Scale the table with g/cylon the x axis and rpm on the y axis. Put spark retard in the middle and setit's mode to average. You should group the axis along the same lines as theyare grouped in the PCM.

We now have a table of the average sparkretard taken out at each timing point. Now go to the table in the PCM andsubtract 75% of this value from the actual spark advance at each point wherespark retard occurred. Re-log the car. Repeat the procedure until no sparkretard is detected. The timing curve should now be tuned.

If the car is an automatic we will now starttuning shift pressure, shift points, and TCC.

5: WOT tuning

The first thing to do is make a quick WOTpass in a low gear (a low load) and check both O2's and knock retard. O2's areNOT accurate or precise at this a/f ratio, but can still be used for a ballparkestimate. If they aren't 850-950 we will adjust the PE vs. RPM table accordingly.This table is where all fueling changes at WOT are made. If knock retard ispresent we need to localize it to a point in the timing table, so using themethod above for part throttle tuning, we will do the same thing for WOTtuning.

If either spark or fuel is changed thengo back and check the other by logging. A wideband O2 sensor is required toaccurately set the fuel map. If wideband feedback is available the a/f ratio willgenerally end the richest at your torque peak and leaning out from there topeak horsepower and then a little rich before and after the shift point forsafety.

Once fuel and spark are set then beginplaying with the shift points and transmission parameters automatic cars. If it’sa manual transmission we are good to go!

Follow-Up

After a week or so you need to re-verifyall your logged values and ensure they haven't drifted. If they have, repeatthe processes necessary to bring them back in line.