MAF will not fail even when frequency fail high is set to zero?

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03-18-2015
Tick

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MAF will not fail even when frequency fail high is set to zero?

I'm tuning a 1999 SS Camaro that has been tuned years ago at another shop. My process is to first disable the maf and dial the VE table in. For whatever reason I can't get the MAF to fail on this car. I've set the MAF fail frequency to 0 Hz and I've set all three of the MAF codes to 'Mil on first error' just like I've done on literally hundreds of other cars but it still will not set a MAF code.

If I un-plug the MAF the car will fire, then stall. It can be started over and and over with the same result and never trigger a code so that I can tune the VE.

Anyone have any idea?
03-18-2015
Bluecat

It has to run long enough to fail the code. Unlike GenIV stuff you cant change the fail counts. Sometime you have to put a reasonable value in the the first cell of the maf table to get it to run long enough to fail. In other words set the 0hz cell to 8g/s so it wont go lean and die before it run long enough to throw the code and kick into SD. Or even a bigger number like 14g/s if its a big cam or stroker motor.
03-18-2015
02statesman

You've got the SES Enable unchecked for the maf codes.
03-19-2015
Tick

Wow. I have literally tuned over 400 late model GM cars with the majority being 4th gen f-bodies and c5 vettes. I have always un-checked the maf codes so that they don't trigger the ses light. The code will still report on every car I've ever tuned. I have also never had to change the maf table in order to give the car time to fail the code. What you are saying makes sense Bluecat, but why out of hundreds of cars have I never had to do this before? I'll give it a shot and see what happens though.

I've had this car run for a few seconds by patting the throttle even with the MAF unplugged and no code set. I've done this and repeated atleast 5 times in a row with no code set. I have never, ever had to unplug the maf to get a 1999 f-body to fail a maf high frequency code when set to 0hz and I've always set SES enable un-checked because if not (on cars that are left SD) it would not pass a NC emissions inspection due to an illuminated SES.
03-19-2015
Bluecat

Setting the first cell in the MAF table to a value close to idle is only relative when no MAF is plugged in. If the MAF was plugged in and sending a signal, it looks up the value in those cells and runs normal with MAF data until it decides to fail, then jumps to SD. Most of the time with the MAF not present and not making the first cell of data "prepped" so to speak, it will just stumble for a second and go on fine. Subsequent restarts dont exhibit it because once the code is throwed it remembers until the next flash. But sometimes it just doesn't throw. Like it wants to see some degree of steady state or something before it makes the call that the MAF is bad. When it does act up they just won't do it. And because its running so rough and/or your pedaling the gas to keep it running it never meets the requirement to fail the MAF.

Leaving the code unchecked is fine. Has nothing to do with 102 or 103 causing a forced SD operation. On GENIII stuff i always do unchecked and 2-no mil for 102 and 103. Usually that works for GENIV too, but on a few ecotecs and a stray g8 or 2 it wouldn't fail unless it was set to 0-mil on first error. And 101 has nothing to do with forcing SD via the hz input, I leave it unchecked and 3-no error. It has to do with the SD and MAF correlating.
03-20-2015
Tick

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I set the first cell in the MAF table to what should be close for idle. I unplugged the MAF. I started the car and it idles fine. No MAF high code will set. If I rev the car obviously it goes very lean because it is still reading the first cell of the table.

Now..... Has anyone ever seen a car that won't fail the MAF under the above circumstances? I know that the MAF shouldn't need to be disconnected to fail the MAF.....and this car won't fail it even when it is disconnected.
03-20-2015
mowton

Quote:

Originally Posted by Tick

Now..... Has anyone ever seen a car that won't fail the MAF under the above circumstances? I know that the MAF shouldn't need to be disconnected to fail the MAF.....and this car won't fail it even when it is disconnected.

So the answer is yes, I chased my tail for 2 days until I did a line by line check against a stock file and found the previous "Pro" tuner had actual disabled the MAF test. Unfortunately it was with EFILive where you can set the voltage at which you run the test, they had it set to 20 so it never ran and by not running it cant fail......

That being said, I offer it only as a way the PCM wont kick over into SD but I am not sure if you can control or disable that function in HPTuners.

Update -- How about if you zero the maximum delta airflow table - P0101? I know, I'm reaching :-)

Ed M
03-22-2015
Bluecat

Lol. You've definitely got an odd one there. I'm with Mowton, it just about has to be that some one before you has change a setting that impacts the ability of the test to run that fails the MAF. From the sounds of it you have done everything humanly possible to make the MAF fail. If you have idled for an extended period in a fairly stead state of operation with the MAF hz reading 0, you should have got a 102 code.

If this is being caused by settings we cant see in HPTuners, like the ones that show up for most GenIV stuff like the fail counts, voltages, and rpms, do you not have the option of just flashing a know good virgin tune from another car to it? I haven't tuned a 99-02 anything in years that I haven't put 12212156 on. There are to many tables and settings we can't get to that can cause little bug a boos and inconsistencies from vehicle to vehicle. I've used 12212156 so much that I know exactly how it reacts to ever situation, and its a familiarity that makes my life much easier from day to day.
03-22-2015
Bluecat

Quote:

Originally Posted by mowton

Update -- How about if you zero the maximum delta airflow table - P0101? I know, I'm reaching :-)

That is a very good idea, if something is keeping 102 and 103 from running, zeroing the MAF/SD delta table and trying to throw a 101 might do the trick.
03-22-2015
Tick

Quote:

Originally Posted by Bluecat

That is a very good idea, if something is keeping 102 and 103 from running, zeroing the MAF/SD delta table and trying to throw a 101 might do the trick.

I tried that also before even creating this thread....

I honestly don't know much about changing to a different OS, I just haven't typically done that because I don't want to create an issue with NC emissions inspections. As long as I could put the proper vin back in I guess it would be fine. I'm sure I could put another file in for a 99 though, or flash in the latest stock GM calibration with my tech 2.

I've got the car for another week so I have some time to mess around with it. It honestly runs/drives just fine running completely off of the MAF. It never occurred to me that there may be some setting changed that isn't visible with HPT. Thanks for help guys.
03-22-2015
mowton

Quote:

Originally Posted by Tick

I tried that also before even creating this thread....

I honestly don't know much about changing to a different OS, I just haven't typically done that because I don't want to create an issue with NC emissions inspections. As long as I could put the proper vin back in I guess it would be fine. I'm sure I could put another file in for a 99 though, or flash in the latest stock GM calibration with my tech 2.

I've got the car for another week so I have some time to mess around with it. It honestly runs/drives just fine running completely off of the MAF. It never occurred to me that there may be some setting changed that isn't visible with HPT. Thanks for help guys.

Can you find someone local who might have efilive to pull your tune?

Ed M
03-23-2015
Pekka_Perkeles

Quote:

Originally Posted by mowton

So the answer is yes, I chased my tail for 2 days until I did a line by line check against a stock file and found the previous "Pro" tuner had actual disabled the MAF test. Unfortunately it was with EFILive where you can set the voltage at which you run the test, they had it set to 20 so it never ran and by not running it cant fail......

This needs to be sticky.

Not that it will always be the way to try to solve the problem.

But for anyone starting a hobby of tuning with HPT, this kind of situation would be right next to a nightmare.

In other words: if I compare STOCK file with modified by other tuning software, I cannot see this kind of difference mentioned in this thread? Or can I?
03-23-2015
mowton

Quote:

Originally Posted by Pekka_Perkeles

This needs to be sticky.

Not that it will always be the way to try to solve the problem.

But for anyone starting a hobby of tuning with HPT, this kind of situation would be right next to a nightmare.

In other words: if I compare STOCK file with modified by other tuning software, I cannot see this kind of difference mentioned in this thread? Or can I?

Thats correct, just like if you pulled a T43 TCM file with EFILive after being tuned by HPTuners, you wouldnt see things like Inertia Factor Profile and its effects on shift firmness or Shift Tourque Adders and its ability to reduce shift torque management.......just the nature of the beast and why I use both.

Ed M