I have a 2005 Avalanche with a couple hundred thousand miles on it. I know I have a pin hole oil leak that burns off on the engine but its not bad enough to leave oil spots in the driveway. Today I was driving and the reduced engine power light came on and went ten mph until I could pull over. I let it sit for a minute to cool down. Once it cooled for a few minutes, I was able to keep going without an issue. The check engine light is on because the gas cap is faulty but there are no other lights on that would cause me concern. I'm just curious if it's a huge issue or if it's the module.. or what it could be. I'm stumped.

 

Search the forums. There are hundreds of other posts about this for all GM.

Well - have you considered there are MORE codes stored now with your check engine light??