engine code: p0420
09-08-2013, 04:14 PM
#1
Racer
Thread Starter
engine code: p0420
guys, I bought a 05 c6, has 105k miles on it. engine light was on for the 02 sensors, I replaced both on bank 1 and only the rear sensor on bank 2, but will be replacing the front one soon. anyways, I still get the p0420 code occasionally and I only get it when im ideling. it says "DTC P0420 Catalyst System Low Efficiency Bank 1". like I said, both sensors were replaced on bank 1 (drivers side). any other ideas? BTW the car is ALL stock.
09-09-2013, 06:00 PM
#6
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St. Jude Donor '08
P0420 is not usually a bad O2 sensor, especially at 100k+ miles. More than likely it needs a cat conv if you're still seeiing the code. The rear O2 sensor is not seeing the readings it should so it's telling you the cat conv is not efficient.
09-09-2013, 11:19 PM
#7
Racer
Thread Starter
sounds good and that makes sense now. im looking at either doing a full exhaust replacement, headers/catted H pipe and rear section, or just replacing both cats with OEM or I see magnaflow ahs direct fit OEM replacement CATS. my only question is, does anyone have experience with the magnaflow direct fit OEM replacement cats? would they cause a CEL?