Any way to fail the MAF sensor before the first start?

When running 2000 F-Body code, the MAF sensor doesn't need to fail to run in speed density...if you just unplug the thing, and set it's codes to no error reported, the car will start and run in speed density mode...and if you run an enhanced OS, it will run off the high octane table.

When running 2002 F-Body code in an 0411 PCM, the MAF sensor HAS to fail. You can disable the SES checkboxes for MAF, and then set them to "0 - MIL On First Error"...which makes them silent codes...but the car HAS to startup successfully first.

What I've found is that, when running 2002 code, if you get another code, for a real problem, and fix it, and clear the DTC's...the first startup, the car will struggle to get to an idle, will stumble, sometimes will stall, and will HOPEFULLY set an SES so that when you turn the key again, it will run in speed density mode.

Is there ANY way to force the PCM to set a MAF fail code before the car is ever started for the first time after clearing DTC's?

I'm currently tuning an 8.1 big block, that I want to run F-Body code on (we converted the engine to a cable throttle body). I've copied in all the 8.1 calibration data (spark, VE, EVERYTHING), and it's VERY VERY hard to get the first start...if I flick the throttle like a madman while it's firing and trying to idle, I can get the transition fueling to keep it stumbling for long enough to set a MAF code, then it runs GREAT, can be shut down and fired right back up normally with no issues at all...but if I clear the DTC's...the first start SUCKS.

Is there any way for me to force a MAF fail DTC to occur before I ever even hit the starter? If not I guess I'll run 2000 code in the PCM instead.

Yes.

In FIRST (0hz or whatever) cell of the MAF table, put like 12-12.5g in that cell and zero the rest of the table. If it starts and looks for the MAF, that will provide fueling for a moment until it fails the MAF. It will make the process transparent.

I don't know why I never thought to try that...makes complete sense, thank you.

Quote:

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Originally Posted by Frost

Yes.

In FIRST (0hz or whatever) cell of the MAF table, put like 12-12.5g in that cell and zero the rest of the table. If it starts and looks for the MAF, that will provide fueling for a moment until it fails the MAF. It will make the process transparent.

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And what if that does not work?

EFIlive has some qualifiers defined for setting a MAF code like min voltage, min engine speed, etc. I didn't have the same problem you are describing until we switched to using HPTuners. The first couple cell trick works, but it still seems to start funny

Mine use to do this u til I got the tune dial in. Now depending on the temp out side. It will start right up, lope for a second or two then smooth right out. I changed some of the start up fueling tables for a lean issue I had and it seemed to fix this problem all at the same time. I use to have to start it 3-4 times.

AFTER CODE WERE CLEARED, TUNE FLASH,BATT DISCONNECT.

Thats not the same problem. This is the first start after a reflash, battery disconnect, code reset.

Yes I know. I happen to run a 2bar setup also. Don't listen it's cool. I'll enjoy my easy start and you can keep bitching.

During normal operation it fires up nice and smooth. No big flare up no lug lug. Just like stock.

I hate to bump an old thread, but I have this exact problem. It's a track car with a ls6 swap and custom 1bar SD/RTT HPT OS. All power is on a cutoff so it loses constant +12V and the MAF DTCs get cleared. I always hit the cutoff when the car is parked. It usually fails on the first start because it needs to relearn the DTCs which only happens on start-like conditions.

Options
1) I looked at EFI Live and it has the conditions (see below) which might do what I need, but don't see them in HPT. Custom OS means I can't just have EFI Live set this up.
2) Put the MAF back in and tune it.
3) Run +12V constant to the battery. I have a really light, small capacity battery which makes this annoying.
4) Fill in the first few entries of the MAF airflow vs frequency table to keep it running before the DTC sets. A bit of a hack and not completely transparent on starts.

Would prefer (1), but the 2.23 beta I have doesn't have the option to change it and the file format does not support a simple hex edit to change those (hidden) entries. Any other ideas?

EDIT: Maybe I can do this. Use EFI Live to setup the fail conditions. Flash that tune to stock tune to the PCM. Read it back with HPT, convert it to 1bar SD/RTT and copy back all the other tables. Not sure if this will work, though, and it's a bit of a hassle.

LABELS
Parameters Value
{C2901} MAF High Frequency Fail 1 13500.000000 Hz
{C2903} MAF High Frequency Fail Limit 12.000000 Failures
{C2904} MAF Low Frequency Fail 1 10.000000 Hz
{C2906} MAF Low Frequency Fail Limit 6.000000 Failures
{C2907} MAF Test Min Engine Speed 300.000000 RPM
{C2908} MAF Test Min Run Time 0.500000 Seconds
{C2909} MAF Test Min Batt Voltage 8.000000 Volts
{C2910} MAF Test Max TPS 95.000000 %

Hooked the 12V direct to a Pb battery on the tender, but as soon as soon as the LiFe battery goes in the PCM will forget. Now I wonder if I can just simulate a start whenever I connect the battery up. Or if there is a way to reduce the time to MAF fail, maybe I can just blip the starter so the PCM fails the MAF without having to get it going over 300 rpm.