I read about the occasional rear window shattering and decided to pull the 30A engine cavity fuse (fuse 10) to prevent it running during remote start. Driving to work the next day, I lost a TPMS sensor (which could be coincidence) and the truck stayed in V8 mode. It's a 46 mile trip, mixed town and highway. AFM was working before I pulled the fuse, and I'm not using a disabler. Is this a known issue? I have a cap and probably won't need the defogger often, so I want to keep it disabled to protect the window.

 

It seems unlikely pulling that fuse caused the AFM to shut off, but the only way to verify would be to put it back in and see what happens.

As for the rear window shattering - I’ve only heard about it being a problem on Ford trucks, not GM.

There is a recall on the rear window heater contacts of equipped with a sliding window - enter your VIN on nhtsa.org to find out if it’s already been fixed on your truck.

 

I would've thought it unlikely as well. My plan this evening after work was to reinstall the fuse and look for the defogger connector. Maybe there's one behind the rear seat somewhere. Leave the fuse, unplug the heater. I hope I didn't mess something up electrically

 

Update: interesting. I replaced the rear defogger fuse and drove home. Drivetrain resumed normal AFM operation and it's behaved normally since. I can't help but wonder if it's just coincidence. But I'm done playing fast + loose with the fuses for a bit. The driver rear TPMS sensor is still not reporting, but I'm reluctant to try to relearn them. When I tried it with our Malibu when one went radio silent I ended up losing all 4. I miss the old days sometimes🤣

 

I was reading up on the AFM in the service manual and it stated that one of the conditions that would cause the ECM to disable AFM is if it’s in “heater performance mode.”

Of course, trying to find any other information about “heater performance mode” has proven difficult thus far, but I’m thinking pulling the defogger fuse somehow triggered it, which then caused the ECM to disable AFM.

As for the TPMS - you can try a relearn if you want, but if the sensor isn’t reading at all, it’s likely the battery is dead and the sensor needs replaced.