The problem seems to be sporadic, I haven't found a way to repeat it. When I start the engine the message center states "high beam out", day time running lights switch from high beam (1/2 power) to low beams, the a/c stops blowing cold air, the a/c compressor cycles on/ off continually, the radiator fans allow the engine temp to rise to the point of overheating. On the instrument cluster, the turn signals and hazards do not work but the arrows on the cluster are partially illuminated. Just had the BCM replaced because of this problem and it’s still happening.

 

year of monte please. a lot of techs are quick to fail a BCM when it can sometimes be a different module in the car. or if they replaced the BCM and didn't program the RPO codes correctly it will screw up the new BCM.
i once changed a PCM on trailblazer and the new PCM was a faulty brand new part it had an internal wiring short.

 

2003 LS Comp 3.4 Thanks for your help! I did watch them go though the reprogram it took a little over 30minutes and everything seem to go fine. I did have to take it to Chevy to mate up the BCM because of the b1001 code. I am leaning towards a relay issue that involve the parking lights and possibly the cooling fan. Are relays intermittent when the ambient temp is very hot?