U0164 Lost HVAC Controls
 

Tablet finally died so reinstalled stock everything except for an aftermarket head unit. During installation process when I had everything disconnected except for the airbag, I had to move my car. About 10 seconds in, CEL came on and threw code U0164 which makes sense because this means the HVAC Control Module (HVACCM) and other control modules on the vehicle are not communicating with each other. Got everything put back together and cleared the code. Now the orange monochrome screen nor the HVAC control unit will power up. Car is continuously blowing warm air. It's almost as if the ECU/BCM has shut down communcation to the HVAC control unit. Rechecked all of the plugs and everything is hooked up correctly including the main white control box under the stereo. Tried unplugging the battery, waiting 10 minutes and plugging back in. Still nothing. I drove to work this morning and it never came on but also did not throw the code again. Any help would be greatly appreciated.

I got U0164 several weeks ago while troubleshooting to help a friend with a backup cam issue. Mine happened after removing and replacing different relays trying to reproduce the problem. I think it was one of the 20279 relays that point towards the firewall from the back of the fuse block. I'm sure there are many ways to get a U0164 code, however.

How did you end up fixing it? Did you lose power to the radio or HVAC controls?

Your aftermarket head unit could be the problem. Try reinstalling the stock head unit.

I just put everything back and cleared it over OBD. Sorry, I didn't test those things before clearing it.

Figured it all out....The plug to the HVAC controls and the monochrome screen on top are the exact same. I had them backwards.

change hvac for example