Heater core went out in my 99 blazer 4x4 4.3 LT. watched a couple videos where the bolts were and went about my way to replace it. i had an issue getting to a bolt on the outside of the firewall and had to remove the PCM. the battery was already disconnected. unplugged got my bolt and finished the job. put everything back together and started it. Here's my issue. All my lights work on the inside of the car. but my gauges only work if i turn my headlights on manually and my odometer is showing anything regardless if the lights are turned on. On my radio and climate control the buttons are illuminated but they are not responding. the screen is not working on the radio either. no sound or anything. i checked all the fuses and still cant find my issue. also my 4wd selector is illuminated but does not function.

 

Wow, something is crossed up. Unfortunately this is basically a hunt. May have to take things apart and start fresh