My 2007 Avalanche is not 4WD or AWD, just plain old 2WD. I can also lock out the stabilitrak but it doesn't stop the error messages or the reduced power. The only thing that works is to turn the engine over several times and this resets the computer.

Before you get talked into replacing the ECM ($1,000.00) I would call GM and open a case with them. That's what we have done.

 

Tom, is this still fixed?

Thanks,
Johnnie

 

Also interested if it's still fixed.
I have an 03 Burb 1500 5.3 (230K miles) and have the Reduced Engine Power issue. I've replaced the APS twice with new GM parts, I've replaced the Pigtail to the TB twice with the recommended $80 part, I've replaced the TB 3 times, once with a NAPA TB and twice with GM TBs, I've removed about 3 feet of wire to the TB and cleaned the grounds, I've replaced the ECM.... The same codes go away for various lengths of time but all keep coming back. My Mechanic refuses to work on it at this point and I'm pretty sure the dealer was just charging me several hundered bucks a pop to reset the codes and send me on the way.

I'm way past done with this thing but new trucks and even used ones around here are crazy expensive and I just put a new Trans in this thing in a fit of optimism, about 15k ago... So I'm really interested to hear if anyone has actually permanently fixed this issue on a 2003-2005 1500, without driving off something high or into something hard.

 

I had this issue with my 03 Suburban. One thing I didn't notice anyone mention is if the power door locks started cycling during this event (reduced engine power, check engine light). Mine did. Dealer couldn't figure it out. They tried a few things that didn't work, I don't remember what they tried, it's been several years. What I figured out was the ground from the rear of the engine to the underside of the hood. Ground strap was rusted and brittle. Sometimes it would make a good connection, other times, not so good and would have the problems mentioned. Replaced the strap with a wider one and sanded the mating surfaces. Never had a problem again. Sadly, the ex-wife totaled it a few years later.

 

I never had the cycling door locks thing on mine. Just the reduced engine power and P2135 and P1515, with P0120 and P1516 sprinkled in for sporadically. I have all 4 showing now.

But now it's not just going into Reduced Power Mode, the engine is shutting completely off... Or rather, it's probably more of a stall in limp mode. Really scary losing power steering etc...

So I broke down and took it in to the dealer, they said it's most likely the wiring harness itself and the engine will have to be completely rewired. Quoted me "about $1000".