Thread: P0421 Code
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Old 08-28-2010, 01:08 AM   #6
snicknc
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Join Date: Aug 2010
Posts: 50

2002 VUE 3.0L
Default Re: P0421 Code

Alright, so I pulled both bank 1 O2 sensors. The pre-cat sensor looked normal. The post-cat sensor had a dark ring (I'm guessing carbon) around the base and a grey-white stripe going from the base over the tip and down the other side.

So maybe some non-sensor safe RTV at some point poisoned it, in addition to running a little rich? I don't think it's still running rich, as I roughly calculated my gas mileage during the 100 miles to be around 23-25 at highway speeds.

It doesn't look like water contamination, as the white is just limited to that one stripe, but I'll probably do a compression check tomorrow just to make sure the head gaskets are good.

I swapped that sensor out with a new OEM one and drove it 100 miles, turning the engine off and starting it back up a couple of times, making turns, braking, etc. No SES light, so that's good I reckon.

At this point, I'm hoping I drove enough to get that "ready" code so I can slam this thing through emissions and get it registered.

For those interested in the non-fouler trick, be aware that it looks like our stock sensors are wider than 1/2", so you'll probably have to use a universal sensor. I couldn't get the sensor to fit in the fouler. I'll throw the picture of my bad sensor on here at some point this weekend just for thoroughness.

To be honest, I'll probably wind up just picking up two universal sensors as well and using the non fouler on both post-cat sensors as I'm honestly pretty aggravated that I'm failing the safety check for f'ing emissions-- especially something as dumb as this code. Over half the counties in NC don't require emissions, but mine does-- lucky me

Thanks for the help so far guys.

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