Last year while driving the temp gauge on the dash dropped to zero and I got a warning on the DIC "Hot Engine Turn Off A/C". Even after letting the car sit overnight and starting it up, I would immediately get the same warning on the DIC. Then after a day or two, the gauge would randomly start reading the correct temp. After it doing this off and on for a few days, I replaced the temp sensor under the alternator. For almost a year, everything worked fine. Then the other day it just started doing the same thing again. This time it didn't start reading the correct temp after driving it for a while. I unplugged the connector on the sensor and checked the connection, and everything there seems to be fine. I checked the coolant level, and it was pretty low so I topped it off. I started the car and again, same warning immediately. I disconnected the battery and started the car up, and the temp gauge started working again. Then while driving to work, gauge drops to zero and same warning on the DIC. My next step is to replace the connector and get a new temp sensor, but before I go through all of that, I wanted to see if you guys had any other things that I should check first. Thanks.

 

You're on the right track. Since you already replaced the temp sensor, you might check the connector and wiring before replacing it again. Look for a melted connector, sharp bend in the wiring at the connector, pinched wire between the alternator and valve cover. I've seen these situations cause an erratic temp gauge and warning messages on the DIC on three different C6s. Let everyone know how it works out.

 

Yep, bank that that the problem is the wire to the connector back halves in the connectors, with either corrosion or the wires cracked instead.

Also, would check the wires back a few feet, since may be a crack in the wire just far enough back that when you where screwing with the connectors, moves the wires far enough back to redeem a problem temporary there (until heat stretched the shielding again)..