Had engine replaced in my 2003 Chevy Tahoe 5.3 Flex. It runs perfect. But if i cut on my ac, hold window but down too long or hold door lock button too long i get message reduced engine power. I get error code P1518. (I have a brand new throttle body and a brand new throttle actuator It doesn’t have any trouble starting) I then gotta use my scanner to reset the code. Any suggestions? Thanks

 

Here's a start. Weak battery is a prime suspect, just because it cranks and starts doesn't mean it's good.

P1518 CHEVROLET code possible causes

• Dead or weak battery
• Faulty Throttle Actuator Control (TAC) module
• Throttle Actuator Control (TAC) module harness is open or shorted
• Throttle Actuator Control (TAC) module circuit poor electrical connection
• Check Throttle Actuator Control (TAC) module connector for water

 

Repairman54 you were exactly right. Got a brand new battery and everything is good. Thanks man

 

Window button was a good clue the battery was tired.

 

I thought it was fixed but its back to doing the same thing. Might be a ground wire