You got multiple problems here

P0420 go to this link: http://www.obd-codes.com/p0420 for the fan speed-check and test the blower switch

Answered by rasmataz
68 questions asked

Thanks for the reply, I'm aware of the Cat code, but I saw an issue online where someone said that code came up when they had the other issues and they were somehow all related but I don't see quite how that is possible. Cat replacement isn't cheap so going one by one with the other issue until it's solved. Usually the culprit is the resistor, and rarely the ignition switch, but both seem fine. I'll look into the blower switch..

Response from cujobob
1 question asked

just to add, i would look close at the connector for the resistor. they fail a lot. replace both the resistor and the connector.

the 420 has no effect on the other issues.
dash bulbs may be failing or the circuit board behind the dash is bad.
check the rear window for broken wires for the rear defroster.

Roy

Answered by ASEMaster6371 (expert)
24,854 answers provided

I've read many issues where all of these symptoms occurred (minus the Cat code) and there was a fairly simple solution each time. I am going to trace all of the wires with my friend who is a retired mechanic, but I'm hoping someone will have heard of another solution for this. Is it all caused by water leaking under the hood cowl through the cabin filter? This specific car had a lot of issues with this type of thing.

Response from cujobob
1 question asked