P0420 fixed with replacing o2 and a/f sensors

[Bijan]

Yo dudes I wanted to share my latest fix. P0420 CEL came on last week. Upon doing my searches, I saw JayROLLA post about replacing the sensors before you replace the catalytic converter.

I looked up the part #s for my 2002 SR5:
234-4261 for the o2 sensor
234-9002 for the a/f sensor

$170 for both on Amazon


At first I was thinking to myself my original ones would be rusted on my exhaust. I sprayed WD-40 on them, let them soak for 3-4 hours, went and bought a mattress, came back, unplugged battery - and to my surprise they came off fairly easy.

EVERY time I work on my truck by myself something seems to break. Not this time.

Anti-seize in the o2 bung. New gasket forthe a/f sensor bung. DONE.

CEL has not come back on after 100 miles of mixed driving.

 

[octanejunkie]

$170 for both on Amazon is pretty good, ya did good :first:

 

[bigtooona]

I bought both for the same issue but could only get the A/F sensor off, and it was brutal. I had to take a Dremel to both nuts they were so rusted on. For the O2 sensor, I bought an offset O2 sensor socket and it still wouldn't budge even with a breaker bar, so I gave up. Code hasn't come back yet. I'll eventually try soaking in WD-40 like you did, but PB Blaster didn't do anything for me.

 

[Drew76]

I just did both of these as well but my 2000 w/Cali emissions had both 2 bolt flange style sensors, guess they changed at some point. Looking at your part #'s above I take it 02 downstream sensor was the threaded one, I only used Denso too.

 

[Bijan]

I just did both of these as well but my 2000 w/Cali emissions had both 2 bolt flange style sensors, guess they changed at some point. Looking at your part #'s above I take it 02 downstream sensor was the threaded one, I only used Denso too.

Yep correct. To my knowledge there is no difference btwn Cali and Fed spec for our 4Runners. Could be wrong - but I think I read that on here somewhere.

2 cats. Sensor closest to engine was technically my air/fuel sensor (upstream yea?) and the one in the middle of my exhaust is my O2 sensor.

I'd bet certain years might have different bungs.

 

[Pedrojr80]

Well im reporting that i also had p0420 code, but i had decided on replacing just the rear oxygen sensor. Today my code came back and i guess at this point im going to have to replace the front a/f sensor. 99 4runner limited with cali emissions and two cats. Any body has that part# handy for the a/f sensor on 99 with cali emissions? Thanks


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