E38 stuck in PE mode and Crazy commanded AFR. Help please!

[brandon6.0]

I have a customers 2007 Tahoe, full bolt on cammed setup. I have it currently tuned in Maf only mode. I have already performed the cruising fuel trim tuning. I just started today making some WOT hit. AFR verified via aem wideband.

What I ran into was the PE fueling would be perfect at 12.5 one minute and thin it would go pig rich at 10s. It would also seem to not exit PE mode. I could make a hit and it would seem to hang at 11s AFR at idle etc. never would return to stoich except when cruising and the O2s brought fueling back. I had to restart truck and it was fine again till I made another WOT hit. U could cruise around with a 14.7afr all day until u made a hit.

Scanner showed commanded AFR of 10.4 while crusing and idle. WOT was commanded 8ish. This is the first ive seen something act like this. I also noticed truck throwed a p101 code once when all this was happening. Maybe a possible bad maf?

If one of u guys could look this over and help I would appreciate it. Here is a log and tune. thanks.


Mods are:


Holley sniper intake 92mm, Longtubes/ORY, BTR stg3 truck cam, Circle D 3400 stall, CAI, 25% UDP and 4.11 gears.

[5FDP]

Make the stoich table all the same value of 14.68, see if it does it again. Worth a shot anyway.

[brandon6.0]

Flexfuel was enabled at first. So i disabled it and ill change stoich as well.

Anyone see anything else tht stands out? What about the pe delay table settings. I wasnt to sure about those. First ive seen parameters like tht.

[5FDP]

PE settings seem okay at a glance.

I know for sure that the open loop tables should not be set to 1.00 for every cell, this is not like the GEN 3 computer. The table is based off of coolant temp and intake valve temp. Gen 3 computers used MAP and RPM which is different.

[brandon6.0]

Yea i know. I just changed them to 1.00 to try and see if it made a diff with fueling. I havnt uploaded and tried tht this tune yet. Im almost certain it want help tho. Ive never had to change it on other gen4s. Always seemed fine with stock settings.

[TCSS07]

make any headway? if your not running flex fuel do what 5fdp said and make the stock stoich all 14.7 because it seems your car thinks it has 75% alcohol since its commanding a 10.4 which is in the 75% cell. your not stuck in pe mode because your car is in closed loop. if you were stuck in pe it would be in open loop. the scanner has a fuel alcohol reset - try and reset it

[5ft24]

Does it have a "failed alcohol content" or "default alcohol content" ? I know the E40 does and if it has an issue with the sensor, it sets alcohol content to the % set there. If its set to 75% and the ECM isn't seeing what it is supposed to see from the sensor, it will be running as if it was at 75% ethanol

[brandon6.0]

I figured it out! I thought i posted back the fix.

I changed stoich to 14.7 all across.

I was looking over the maf sensor figuring it was bad bc it would idle and act right with the sd mode only.

With maf i couldnt get it to start up and run. Ended up being a gap on the cai tube on the bottom side of the tb. Tube had slipped off the tb basicly.


I retightened it up and all is good to go. 14.7 afr cruise. And 12.5 afr Wot! Thanks for the help guys!

Stupid simple mistake lol!

[SultanHassanMasTuning]

2007 Tahoe 5.3-60e BTR Stg 3 cam, Longtubes-Modified tune () try this.hpt