Code 0420

[bluewasp]

I have changed exhaust from header back. Each time I clear the engine light it will reappear after a few miles. The code is 0420 which denotes inefficient cat. Has anyone else had this problem? Hindsight states should have not changed cat. Will a new O2 sensor be a possibility for solving this? Thanks for any replies.

[gonzomania]

Have you disconnected the negative battery terminal for awhile so it can reset the computer?

[bobs turbo pt]

yes try the reset of the computer that might do it

[bluewasp]

Have reset several times, light returns each time after a few miles.

[Wicked_PT]

quote:Originally posted by bluewasp

Have reset several times, light returns each time after a few miles.

Are you sure your Cat is not installed backwards? It is an easy mistake that some people make. There should be an engraved arrow on you Cat and it should point towards the rear exit of the exhaust. If the arrow is pointing towards the headers, then it need to be flipped around. You O2 sensor could be on the wrong side of the Cat if it is installed this way. But it is posible that your O2 sensor is burnt out as well. There are 2 O2 sensors, one on the header, and 1 on the Cat.

[bluewasp]

Good point, will put it on the rack this week. Thanks

[bobs turbo pt]

did you find out what was wrong ??

[bluewasp]

The cat was installed correctly, will try an O2 sensor this week.