I just got my CEL checked at Advance Auto. I have a P0420 code. Bank 1. I realize this could be the cat or it could be an O2 sensor. Back story: I bought the car with a CEL. Had it checked and it was an evap code. I changed the gas cap because, well, it was 14 yrs old and didnt look very good. The CEL went away. Great! So last week Im driving along and suddenly the car starts misfiring like a sumbish. CEL is flashing and it runs like crap. Turns out, it was the coil packs. Decided to replace the ICM, coil packs and housing, and new spark plugs. Crank it up, it runs fine and the CEL goes off. Again, great! A few days go by and the CEL pops again and here we are today. So any ideas/suggestions?

1997 Sunfire GT 2.4L 131000miles

See if you accidently unplugged the rear O2 when you did your ignition work. Other option is a cat that could be going bad or O2 like you mentioned/

Located at the rear of the vehicle next to the gas tank, is the EVAP canister. There is a two wire plug that runs from the top of the evap purge selenoid to the harness entry point into the car. The connector is a four pronged connector, but only has two wires. It is approx. 8 to 10 inches in length? This wire harness has a tendency to corrode and break. Can only be purchased thru the dealer. (no aftermarket parts available) This wire harness is the demon that creates most of your cars EVAP codes.

dan oestereich wrote:Located at the rear of the vehicle next to the gas tank, is the EVAP canister. There is a two wire plug that runs from the top of the evap purge selenoid to the harness entry point into the car. The connector is a four pronged connector, but only has two wires. It is approx. 8 to 10 inches in length? This wire harness has a tendency to corrode and break. Can only be purchased thru the dealer. (no aftermarket parts available) This wire harness is the demon that creates most of your cars EVAP codes.

Except for the fact that P0420 is not an EVAP code...



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