I'm so fed up with this issue. Got a 2004 Silverado 2500 2 years ago. About a week in it goes into Reduced Engine Power. Of course this is a known and common issue. So we take it back and they work on it and replace the throttle body. This worked for a month or two. But we noticed that the speedometer started going out then the reduced engine power started happening as well. We took it back and they said that they replaced the Accelerator pedal sensor. The truck ran good for awhile, although the speedometer is completely not working ( the rest of the gauges work fine though). Well my fiance drove the truck from Texas to New Jersey about 3 month ago, about half way there it started back up doing the reduced engine power. Once in NJ he replaced the spark plugs and cleaned the mass airflow sensor. Again the truck seemed okay for a bit. I went to visit him last weekend and the truck just continued constantly with the reduced engine power issues. He barely hits the gas and the truck is doing it. We replaced the Accelerator pedal sensor since it seemed to have not been replaced as they claimed months back. But once we did that now it is permanently in reduced engine power. It used to go back to normal if he shut it off for 10 or 15 minutes. Somebody, please, for the love of god help us. I don't know what we should do next as it seems that nothing we do will fix it! I'll answer any questions you have if you need additional info. Thanks!

 

Was this issue ever solved I've got the same issue with mine that they can't figure out because it is so intermittent, I'd like to know where to go next.

 

I Also have a 2004 but mine's a suburban 5.3 1500 and it's been doing the same thing so right now it's doing it and it wasn't doing it permanently but now it is I had a climate coolant sensor I replaced fixed it while the clip harness was broke and I was driving it that way and finally I replaced it and then quit all together so now it's all the way reduced engine power I'm trying to figure it out right now myself but it seems to be a common problem I wonder what it is so I thought about going out and taking all the plugs out and going that route I know it ain't the sensor cuz I tried it in hot water and cold and the voltmeter and it was good