Help fixing P0420

[S Brake]

I have a 1996 Limited with one cat and two O2 sensors.

I've searched a bit but am still unclear on some of the steps to finding the real problem behind my P0420 code. I'm aware that the code is triggered by the rear O2 sensor but I'm not sure if the sensor is bad or if it is the cat. I saw somewhere about adding a spacer to the sensor to determine the problem but I'm not clear on what kind of spacer to use on the flange-type sensor. Any help on what I need to buy to figure this out would be appreciated.

 

[nissanh]

I think that's the spacer used to extend the spark plugs. You should be able to buy it at the Autozone for about $5 or less. You'll need two for the project.

Try this at youtube
"Clear check engine light for less than 5 dollars"

 

[S Brake]

The problem is that because the 3rd gen has the flange type O2 sensors, I don't think these spacers will work. Has anyone with a 3rd gen successfully used these spacers?

 

[Stick Figure]

yeah non-foulers won't work on the older Toyota stuff.

 

[S Brake]

So will I have to order a new sensor to see if that fixes the code?

 

[TheDurk]

So will I have to order a new sensor to see if that fixes the code?

If the sensor has 70k or more and there are no obvious signs the cat is toast (it rattles badly from the inside, gets red hot, or has a sulfur smell) and you have checked for exhaust leaks; replacing the sensor will cost you less than any diagnostic to tell you if it is the sensor--and then you will still need the sensor. At 70k+ it doesn't owe you anything. So just do it.

If you go to a dealer they will tell you P0420 means cat is toast. I cured my p0420 in 2009 with a new rear sensor.

 

[S Brake]

If the sensor has 70k or more and there are no obvious signs the cat is toast (it rattles badly from the inside, gets red hot, or has a sulfur smell) and you have checked for exhaust leaks; replacing the sensor will cost you less than any diagnostic to tell you if it is the sensor--and then you will still need the sensor. At 70k+ it doesn't owe you anything. So just do it.

If you go to a dealer they will tell you P0420 means cat is toast. I cured my p0420 in 2009 with a new rear sensor.

I'm at 141k so I figured a new sensor would be what I need. I just drove around with the rear window down and I couldn't smell any sulfur. I don't think i have an exhaust leak. I've only had the car a couple weeks so I really have no clue how long these sensors have been in.

 

[4R99JB]

I agree that there is probably nothing wrong with the cat; after they charge you for a replacement, they will dip into the huge profit to change out the sensor too, but you'd not know any better. But then again they'd probably just charge you for the sensor too saying that they were both bad.

Cats usually only go bad because of physical damage and EXTREME temperature changes like driving hot exhaust through freezing water. The material inside is like ceramic and would breakup resulting in the "rattling".

Good luck. :nerd:

 

[bitchaaz]

Cats usually only go bad because of physical damage and EXTREME temperature changes like driving hot exhaust through freezing water. The material inside is like ceramic and would breakup resulting in the "rattling".

Good luck. :nerd:

So lets say theoretically, there was a bad Hurricane that hit the east coast. And I had to drive in it, going through puddles and flood waters. Is it a coincidence that the P0420 code kicks on a day later? I don't hear any rattling at all. 221k on the clock.

 

[S Brake]

As an update to my CEL, I replaced my starter a couple weeks ago and had to disconnect the battery in the process. This obviously cleared the CEL. That was two weeks ago and the light still hasn't come back on. Previously the light would come back in a couple days after clearing it with an OBDII scanner. I'll post again if it finally does come back on.

 

[S Brake]

It's been over two months and my check engine light just came back on with the same code. Next step is to replace the rear O2 sensor.

 

[vincer77]

I got this on my son's 4runner. I replaced both sensors and the code has gone away. Have almost 150k on the clock and do not know when or if they were replaced. Now I know.

And I heeded the advice on the board and bought the Denso sensors.

 

[iowajosh]

It's been over two months and my check engine light just came back on with the same code. Next step is to replace the rear O2 sensor.

A denso>?

 

[S Brake]

A denso>?

Yes, ordered a new denso O2 sensor from Amazon last night, $55 shipped.

 

[S Brake]

New O2 sensor installed. The nuts were very rusted and rounded off so I had to use an extractor set. The old gasket was completely rusted to the exhaust and I had to chisel it off.