What is the year of your Volt? How old is your 12V battery?

 

2017. I still have the original 12v battery.

 

Probably not the cause, but, I would replace the coin battery in the fob and clean the contacts for the battery. Even with a new battery in my fob, I have to tap the fob sometimes to have the car recognize it.

 

Thanks Jbaker, My FOB batteries are fairly new. In my OP I mentioned car lights when using the FOB. When I hit "Lock" the lights flash. (So FOB batteries are working). Then I hit the "Precondition" button normally the running lights come on and stay on. In my case the second lights didn't come on. A precondition failure that sets the engine light. This has only happened twice so far, and only when it's cold.

 

old post answer from WOT

"Well there MUST have been another DTC. P0AC4 isnt really even considered a "fault" code, as it will automatically set in the Engine Control Module (ECM) whenever some other system significant fault s detected within either of the Hybrid Powertrain Control Modules (HPCM1/2). Since the ECM is really the only module permitted to turn "ON" the Check Engine/ Malfunction Indicator Light due to OBD2 regulations. When the HPCM detects a system problem it essentially "tells" the ECM to set the P0AC4, basically JUST to turn on the MIL. So this code is always set in combination with some other DTC.
Did Onstar even mention another code? Did you write them down? "

 

Thanks Cord, yes there were other codes. P1AEE and P1AEF.

Not using Onstar. I have a OBD2 bluetooth reader to get the codes and delete them. Whatever is causing this does not affect the operation of the car at all.

 

see this thread: Got these three codes New Years Eve.

 

Thanks Danno, KNI.

 

For future reference, for ALL factory equipped remote start vehicles, if the check engine light is on for any reason, remote start is inhibited. This behavior is an emission regulation, not a remote start problem.

 

Thanks Chevy Tech!