mirror temperature reading

Have an 02' trailblazer. The inside rearview mirror has Onstar, compass and outside temperature display. Everything works fine except the temperature display. All I get is "OC" or "0C". Why is this and how do I correct it.
Thank You

I didn't know that the temperature reads in the mirror, i thought it read on the center where the heat/ac controls are. but i think that its the compass and it might need to be recalibrated....try holding the power button for a couple seconds (up to 15) and drive it around for a few miles...that should work..if it doesn't then it might be something wrong with the computer???? idk..hope this helps

oh yea...forgot to tell you. when it is cold outside (below 0) the compass does not work accurately. so weather might also be a problem...

OC = Open Circuit. the temperature probe has probably gone bad. Unplug the temp probe (should be behind the front grill) and use a paper clip to short across the connector. If the probe went bad the mirror should now read SC= Short Circuit. If it still reads OC, the wires are cut or corroded some where. Easy test. Probes available at your local dealer.

Thank you, I'll try it.

Anyone have a good diagram of where it is behind the grill?
Mine did the OC once under warranty, and has started doing it again intermittently, and in the summer the temp reading is way off when it actually shows a value. this winter it appears to be more accurate. I'm hoping reseating it might work