I just noticed it is coming on EVERYTIME i hit the brake? So when the brake switch activates, the light on the switch comes on. This can't be normal. There must be a short or something, but HOW is the defrost tied into the defrost?

Also, what in the world is the EGR diag switch? My car threw a code 42 and my scanner siad the egr diag switch wasn't significant. I notice this code only sets at highway speeds and a constant RPM, and also noticed that what my scanner calls the diag switch in the data, NEVER opens. It always stays closed. The EGR valve operates good, and is new. I could see it ont he data screen operating. My guess is the diag switch is the EGR solenoid?

 

1. Chec the ground connections for the rear glass. There is a good chance that one of the connections at the lower end of the nitrogen gas springs has failed.

2. The diagnotic temperature switch is mounted to the base of the EGR valve - Or at least it WAS mounted there on the old valve:

 

Yeah i replaced that too, all i thought it was called was the temp switch. thanks. Im gonna replace the solenoid since its all thats left lol.

 

The code 42 probably doesn't mean the temp sensor is bad, just that when EGR is commanded that it doesn't see any temp change, likely due to a problem with a) solenoid, b)EGR stuck shut, c)vacuum control lines for EGR. I'd check the vacuum lines first. If those are fine, run the engine and use a vacuum pump to manually open the EGR valve at idle, and see if the engine starts to run like pooh (which means the EGR valve works). Then measure the resistance of the solenoid. If it's open, it's bad, and will just support your decision to replace it. If it has some resistance, than it might still be bad, but maybe not. Might be the wires that control it. Might be the temp sensor wire also.