Swapped PCM leading to low LTFT and idk why!?

**Jrjrman** · 10-31-2018

Okay so I have a 2008 Grand Prix which, for some reason, isn't compatible with HP Tuners. To get around this I sapped out my 2008 PCU with one from a 2006 but even since I did the scanner is reading really low fuel trims when I'm at or near idle and I don't know why. I can't figure out for the life of me what is different between the 2006 and 2008 that would cause this??? Please help!

**Scottydoggs** · 10-31-2018

have you checked if your maf is the same part number as the year of the pcm? might just need the maf turned up.

**Jrjrman** · 10-31-2018

I think so but how can I check?

**Scottydoggs** · 10-31-2018

go to rock auto and search for a maf for your car and the donor pcm's car and see if the part # is different. if it is, thats the issue most likely.

**Jrjrman** · 10-31-2018

Yeah they're both the same

**Scottydoggs** · 10-31-2018

you can take some fuel from the maf. just a little bit in the lower areas, 1000-3000 is idle range, 3-7000 is cruise, 7 to the top is wot.

**BillBoost37** · 10-31-2018

Have you compared the two bins for fueling and airflow? GM changed some stuff from year to year and if you look..likely you can find it and copy the table in.

**Fivefingerdeathpunch** · 10-31-2018

2008 was a year only computer/calibration as they started the switch to can-bus, that is why it was never supported. Not worth their time to make a editable file for 1 year.

**Jrjrman** · 11-01-2018

What does that mean?

**Jrjrman** · 11-01-2018

That's what I was thinking but I don't know where to find a stock tune file for a 2008.

**Scottydoggs** · 11-01-2018

its time tp learn maf tuning

**Fivefingerdeathpunch** · 11-01-2018

There are no 2008 V6 stock files, nobody ever created one.

DHP and HPT never supported that year so nothing is available.

**SgtMarshal** · 11-01-2018

should have bought a GXP

**Jrjrman** · 11-14-2018

Okay I tried tuning the MAF table and it looks like that helped.

**97gtp01gt99gt** · 06-13-2019

So do you tune pcm looking to get mines done or order one from zzp got p0171 running lean stft is about 20.3 and ltft 16.3 Ik those aren't right no leaks changed fuel filter no luck

**mguzzo** · 06-13-2019

Originally Posted by 97gtp01gt99gt

So do you tune pcm looking to get mines done or order one from zzp got p0171 running lean stft is about 20.3 and ltft 16.3 Ik those aren't right no leaks changed fuel filter no luck

with those lean trims, you probably have a vacuum leak. check again.

Thread: Swapped PCM leading to low LTFT and idk why!?

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