Po420

[alp]

I've got the CEL ON. The SCII reads PO420. Made the search and found that more likely O2 sensor(s) to be replaced with new DENSO's ones.
Now I have a question: how to find out if my 99 SR5 has a California emission
or 49-states? That will affect the DENSO part number. It looks like my truck has 2 cat. converters - well, at least I see 2 units before the muffler. But the truck was bought in NJ not in CA or NY. The Title doesn't say anything about Cal spec.
Thanks for advice!

 

[alp]

Anyone?

 

[Nelsonmd]

If you have CA emissions, then there should be a sticker on the under side of your hood stating that. It may still be Cali emissions if it was bought elsewhere. And if you have 2 cats, then you definitely have CA emissions.

Honestly, I wouldn't worry about it too much. I have had P0420 since I git mine, and I don't plan on fixing it any time soon. Just clear the code when it comes up, which is easy with the SGII (I've got it too). I even managed to get inspected. I cleared the codes, drove it until all but the CAT test had finished, and they passed me anyway.

 

[alp]

Thanks Nelsonmd!
I still plan to replace O2 sensors and see if it will clear the code.
I hope it is not too late and I don't need to buy new cat(s).
As I understand from different posts the bed O2 sensor(s) will decrease the gasmileage and can eventually ruin the cats.
On a side note: the exhaust smells terrible. Can it be an indication of the failed cat?

 

[VA07]

Thanks Nelsonmd!
I still plan to replace O2 sensors and see if it will clear the code.
I hope it is not too late and I don't need to buy new cat(s).
As I understand from different posts the bed O2 sensor(s) will decrease the gasmileage and can eventually ruin the cats.
On a side note: the exhaust smells terrible. Can it be an indication of the failed cat?

The exhaust smelling bad can be a sign of a failing or failed cat.

I was under the impression that the p0420 code had nothing to do with the rear sensor being bad but had to do with the Cat efficiency. I thought the code for the rear sensor being bad was a p013*.

I would probably get a SGII and look at the readings from the rear O2 sensor before spending the money on a new sensor to ensure that the sensor is in fact malfunctioning.

If you don't have emissions testing in your area you could go with the URD simulator. You still need to have a functioning rear O2 sensor, but it will "correct" the signal to believe that the cat is functioning efficiently.

 

[TheDurk]

The exhaust smelling bad can be a sign of a failing or failed cat.

I was under the impression that the p0420 code had nothing to do with the rear sensor being bad but had to do with the Cat efficiency. I thought the code for the rear sensor being bad was a p013*.

I would probably get a SGII and look at the readings from the rear O2 sensor before spending the money on a new sensor to ensure that the sensor is in fact malfunctioning.

If you don't have emissions testing in your area you could go with the URD simulator. You still need to have a functioning rear O2 sensor, but it will "correct" the signal to believe that the cat is functioning efficiently.

This part in bold is incorrect. There are specific codes for the sensor that relate to specific defects, such as an open heater circuit or out-or-range reading. However, a rear sensor can be degraded and lead to a p0420 and no other DTC. This is why it is listed in the cause list under P0420 in the FSM. If it has 70K or more just go ahead and replace it, the rear ones aren't that expensive and they do go bad. I replaced my rear sensor due to a solo P0420 at 113k in March of '09 and have not seen a P0420 since. (Well, one last August going at slow speed through a large crowded park on a Sunday for about 20 minutes--cleared that one and it never came back,???).

To the OP: The rear sensor should not have any serious effect on performance or lead to a rich or lean condition that will kill the cats. It does not affect engine operation directly as opposed to the front one where this is most definitely the case. Gadget, the guy who sells the sim, says the ECU does use the rear sensor for periodic re-calibration of the front one, but it is hard to say what effect this has. I'd love to know.