I posted up about this on HPT forum last night and its had no responses. The guy wants the truck done stat, so I want to figure out whats going on. In short, its a 2012 Colorado with the ZL1 engine/harness. Here's what its doing:

-With key off, TPS reports 30% until you tap the throttle. TPS goes to ~15% for a few seconds and then returns to 30%

-After startup, it idles fine until you touch the throttle. After touching the throttle, idle jumps to ~1500rpms and idle adapt advance freezes wherever it was at when the throttle was touched. Also occurs while driving as it tries to push through the brakes at a stop while in gear.

-No power enrichment. It knocks up a storm even out of boost. Commanded AFR never changes from 14.68.

-Sometimes at idle it will open the throttle to around 31% and pull 24° of timing to try to maintain idle speed. Spark is occurring past top dead center at that point.

-REP mode while driving. Seems to occur after getting back on the throttle ever so slightly after letting off when cruise speed is reached.


None of this is pointing to any particular issue. I would try a new ECM, but its $100 to license and I am trying to avoid expenses from guessing and checking if they aren't going to work. Any ideas, or has anyone experienced something similar?


Some pics for anyone curious:

 

what ECM doesn the ZL1 use E38?

Also, is it the stock tune?

It sounds like its trying to compensate for something its missing or its getting some wrong info from some where? Harness issue?

Grasping at straws too and thats the first questions i thought of.

 

It has the E67.

 

Tranmission?
it also sounds like it might be thinking its moving? VSS?
like the cruse control/throttle follower?

 

Is he using the colardo gas pedal or the ZL1? I would look there...

 

Thats true... also the TAC module?

 

It is using the ZL1 pedal. Here's the log from last night just sitting with it in park and seeing what it does. The VSS doesn't move from 0 the whole log. But you'll see some craziness at frame 3447. Thats where it decides to open the throttle more but retard timing simultaneously to try to maintain idle. Nothing was done to make it do that, it just happened on its own. Also tried swapping out to another throttle body and still did the erratic 15-30% stuff.

 

sounds the ecm is getting pissed off for some reason.

as far as the pe trigger. have you tried setting the tps trigger 15 % or so to see if ti triggers it? 15-20% would read out to be -5hg to 0 on the boost gauge.

bad *** swap though! looks factory

 

I have dropped PE values low enough that it should be in PE at near idle. No change.

 

What's the a/c request doing while this is happening? Is the a/c functional and cooling?