I have 2001 Silverado 2500 that has the rearview mirror with onstar/compass/temp reading, and for some reason, it has started showing around 10 degrees low. The only thing I've done was disconnect the battery for a couple days while I was installing a radio. Has anyone here had an issue like this?

I've replaced the sensor behind the grill, and did the recalibrate for the compass, with no luck. I've also disconnected/connected the battery trying to reset it. Nothin. Is there a way to recalibrate/adjust the reading?

 

Are you sure its off? Usually it reads high because of engine heat...

 

What are you basing your temp off of to assume it's off. The best way to test the sensor is take a cup of half ice half water and let it stand for ten minutes or so. Then if you have a thermometer dip it into the water and get a stable reading then drop your sensor in and see what the rearview says. Generally you can expect + or - 3 degrees from that temp.

 

I've compared it to 3 other vehicles and a therm at my house. and it's consistently showing 10 degrees cooler than the actual temp. Could be a coincidence, but it was correct up until I changed out the radio. Don't know of anything I could have changed there though, it was pretty much plug and play. hhmmm

 

The mirror display gets its input from the thermistor mounted near the power steering cooler on the front of the radiator. If that falls, breaks, or is moved somehow from the very exact position GM has it in, your compass temperature will be skewed slightly.

 

So, I did a little more research, and looks like the sensor connects to the BCM, then the BCM decides what the display should read. So, my question now is, is there a way to reset the BCM without a Tech 2 tool?

 

You could pull the battery cable again and see if it resets. That's the only way I know of to do it though.