Originally Posted By: Vikas
Quote:
The good news is that most car makers don't put too much stock in the rear O2 sensor. Cynics would say that the rear O2 sensor is included simply to make a vehicle OBD2 compliant. The front O2 sensor is important - it runs the engine. The rear O2 sensor is mostly along for the ride.
Given the relative significance of the rear O2 sensor, there are a variety of equally significant work-arounds in case you start generating P0420 codes - everything from a spark-plug anti-fouler (the $5 fix) to simply deleting the P0420 code from your ECU, if you have an open port reader/writer. You can also citrus-clean your cat. There is a fair body of evidence that vehicles showing a P0420 error will still pass a tailpipe snorkel test. That is, they are not polluting.
I agree with every single statement. However, there is nothing "cynical" about it. This is how the system is designed. This is why putting fresh new rear O2 sensor at the first sign of P0420 is so stupid and counterproductive.
Usually, a new rear O2 sensor will do no good.
And, if you take the vehicle to the dealer, the dealer really has on two or three repair options - replace the rear O2 sensor, replace the front O2 sensor or replace the cat. Replacing the cat is not a pleasant option, unless it's under warranty. OEM cats are deathly expensive. Even the front O2 sensor is fairly pricey. Replacing the front O2 sensor might make the engine run a bit better, so it's not a total waste, but it generally won't solve the problem.
The $5 fix solves the CEL code problem and leaves the OBDII codes ready. If you delete the P0420 code from the ECU, a sharp-eyed inspector might balk. Maybe, maybe not.