Cat inefficiency code, swapped cat, need help!
Thread Starter
Staging Lane
Joined: Jul 2010
Posts: 93
Likes: 0
From: Kenosha, Wisconsin
Cat inefficiency code, swapped cat, need help! i recently took my car to a shop to get some wiring fixed, and they gave me my 02 ss back with a flat tire and a cat inefficiency code. my buddy has a firebird with full exhaust so he let me have his old cat, which was working perfectly when he took it off. it was the bank 1 cat, so i switched the bad one out with the good one. but im still throwing the same code. i also replaced the bank1 sensor2 im early summer. i have stock manifolds, cats, and y pip with slp lm. what are the chances its the 02 sensor? or anything else?
Unless it is a bad cat, it is likely either a bad sensor or bad wiring/connector/ground. What wiring was the shop working on?
Swap in a know good sensor and/or trace the wiring with special attention to the connectors. Finally check the engine wiring harness grounds.
Swap in a know good sensor and/or trace the wiring with special attention to the connectors. Finally check the engine wiring harness grounds.
Thread Starter
Staging Lane
Joined: Jul 2010
Posts: 93
Likes: 0
From: Kenosha, Wisconsin
they fixed some wiring that had to do with my engine sensor fuse blowing. so it was wiring on the circuit of the 02's, maf, and skip shift. according to them they had nothing to do with any wires that have to do with the cat. but before my car would throw codes for some 02 heater circuit, skipshift malfunction, maf low input, and 3 bad 02's. would 02 sims make the cat code go away so i can pass emissions?
A P0420 or P0430 can only be caused by one thing: an inefficient catalyst. IT CANNOT BE CAUSED BY ANYTHING ELSE. That includes O2 sensors, wiring, exhaust leaks, etc.
You say the code is still present? Well, did you try clearing it?
Just take the car to a GM dealer regardless. As long as you have less than 120K miles on the car, they will replace it free.
You say the code is still present? Well, did you try clearing it?
Just take the car to a GM dealer regardless. As long as you have less than 120K miles on the car, they will replace it free.
Thread Starter
Staging Lane
Joined: Jul 2010
Posts: 93
Likes: 0
From: Kenosha, Wisconsin
well i put a good cat in, and the code came back right after i cleared it. what else could it be then?
and im bringing it to a dealer on monday to see what they say about replacing them.
and im bringing it to a dealer on monday to see what they say about replacing them.
A P0420 can be thrown if there is severe enough misfire that the Cat just cant handle all the raw fuel. While the cat is usually the culprit here, it's not 100% always the cat. Also, if you have a faulty B1S1 showing incorrect readings, then sensor2 is thrown out of whack, which can also pop a P0420, but making it think the cat isn't doing it's job. Work at a shop that does a lot of custom exhaust work and run into several P0420's that have been fixed by a B1S1 replacement, or on the extreme cases, a simple tuneup.
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