: PCM code????

01-06-05, 10:04 PM
I pulled the codes off my DIC (my SES light is on) and came up with a PCM 0420 code and 5 AMP codes. I looked up the AMP codes but couldn't find anything on the PCM. Anyone have an idea? Thanks.

01-06-05, 10:46 PM
TWC System Low Frequency-

This is thrown by the computer when the Catalytic converter is not working as efficiently as it should. Basically it means the Oxygen Storage Capacity of your cat is lower than it should be, causing a drop in performance resulting in higher emmisions. Aparrently, it does this by running the Air/Fuel ration lean and then rich again. The computer measures the difference between the front O2 sensor and the back O2 sensor in the cat. If the difference between them take a while to change, then the cat is storing the proper amount of oxygen to brake down the hydrocarbons. If it's too short, then the computer will set the code, meaning the cat's efficiency has dropped. This is in lamens terms, what it says in the book is rediculous. Take it to your dealer and ask them if they can test you catalytic converter. If it's bad, don't buy it from the dealer, it's expensive as hell. I looked it up, and apparently it only comes welded together with the rest of the exhaust system List price is $1052.00, but this site has it for $789.00. I would suggest going to the dealer first and seeing what they say. Good Luck.

01-07-05, 03:35 PM
Dan, thanks again. The car only has 35K on it, aren't cats supposed to be warranteed for 100K or something? Although knowing GM they'll probably void the warranty because of my Corsa system. Does anyone know if a high flow cat is made for the STS?