4forall

well i completely disreguarded the CEL b/c he knows why its being thrown, the cat.

nartnailuj

how do you reset the ecu? unplug the battery? im getting a new intake soon, should i reset my ecu?

4forall

you do it by removing the fuse in the panel of the driver side of the car under the dash. you pull the ecu backup fuse for a few mins and then put it back in.

kaissi

Or unplug the battery positive plug for few seconds too

nartnailuj

so i should reset it after i install the intake? or it wouldnt make a difference?

SgtB

It doesn't do anything. Most of the time it just takes the ecu that much longer to self correct. A bad tank of gas will not lock the ecu into a low performance mode. It will correct itself. I'm not talking out of my ass. If you want to take my advice as an insult I can't stop you.

No need to reset for an intake.

B serious

Your CEL is on for a cat...but you think the cause is the leaking resonator...which is AFTER the cat?

I think something else is going on. I wouldn't keep justifying unrelated issues and using bandaids. Fix the problem....not the symptom. Fixing the symptom is like thinking cough syrup is the cure for bonchitis.

aCab

I actually had the resonator removed last year and a few days after I had that done, the CEL came on for the first time. I guess it could be just coincidence, but from what I've read, you can get a P0420 from an exhaust leak as well. I may very well be wrong, but from what I understand it could be whats causing it.

I'm installing a test pipe next week and just registered my car at my apartment at school rather than at my parents house, so I'm not going to have to pass emissions anymore. I am going to get them to re-weld the pipe that I had installed in place of the resonator at the same time to fix any future problems.

Just an update on the ECU reset - I put 250 miles on yesterday just running errands around Central Georgia, and still haven't had the CEL come back on (knock on wood). Car is still running great and idling perfect - better than I ever remember it. Reminds me when I used to tune the carbs on my old Jeep back in high school - really rewarding.

For now, it seems like everything is peachy...unfortunately my throwout bearing is rattling a little bit Guess it's time to do some clutch work.

B serious

A cel for a cat can come on because of an exhaust leak if the leak is BEFORE the cat. Not after it. Your exhaust is one big exhaust leak if you think about it. there's two big holes (tailpipes) after the cat.

mister x

IIRC the P0420 code flags cat inefficiency by measuring the differential between the primary O2 sensor in the header collector and the secondary O2 sensor in the cat itself. It would seem to indicate the problem is someplace between the two sensors.