Ok...everyone. Here's one that's stumping me. Before, I describe, know that I've already thrown a good amount money in repairs and new parts at this problem.
So, my issue is the truck running fine and out of nowhere lights up the dashboard with both the 'Check Engine' plus 'Reduce Power' lights. And, does go into a reduced power mode. Along with running real rough.
Initially, it was giving Throttle Body type error codes. Which had ne change out the TPS three different times. And, the actual Throttle Body twice. Plus, I changed out the Pig Tail part of the wiring, as well.
No success!
Then, after some research, I started replacing air intake parts.Air Filter, MAF Sensor.
Still no succes!
The interesting thing about this problem is that it seems to happen much more frequently during cold weather. Like 40s and below???
Anyway, looking forward to suggestions !

Socal8

'02, 2500HD, 8.1L, 4x4, Allison, crew cab, LS

 

This sounds tough. I had something like this happen before. Check the ground wires and battery cables. Make sure all are clean and tight. Bad grounds can cause strange problems.

Also, check the wiring harness near the throttle body. Sometimes wires rub and break inside the cover. Even if they look good outside, they could be bad inside.

Since it happens more in cold weather, maybe there's moisture getting into a connector. Try checking the connectors for rust or water.

Last thing — scan it when the lights come on. See if any codes come up right then. That might help narrow it down.

Hope you figure it out soon.