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Unread 04-09-2013, 10:11 PM   #1
kpalm7
Registered User
2006 LJ Wrangler 
 
Join Date: May 2011
Location: Reno, NV
Posts: 62
O2 sensor issue...

Hello,

I recently upgraded from a '97 TJ to a '06 LJ 4.0. The LJ has been sitting in the snow for a couple years so there's several leaks to address, but for $4500 on dana 44s with an e-locker rear, high pinion front spooled with coilovers, two sets of 35s, and a hardtop, there was no way I could pass it up.

Anyways, to the problem. It's had a check engine light since the day I threw a new battery in it and brought it home. Originally it was P0431, which many have found was a bad catalytic converter. I'm at 79,550 miles, so I'm hoping to get the O2 sensors working properly before 80k so the dealer can pay for my new cats under federal warranty requirements. I figured to make them more likely to get to the cats, I'd replace all four O2 sensors with new NTK ones. All went well except the front downstream sensor, as it's connector had melted from touching the exhaust. Not a problem, I thought, I'm perfectly capable of soldering on a new connector, so I ordered one at the local Stealership, and soldered it in today. Plugged in the new O2 sensor that I had screwed in last Friday, reset the code by leaving the battery unplugged, and assumed I'd be good to go. Not so much. Within three miles I got a P0138 code, pointing to a voltage issue with that exact O2 sensor. Reset it just to make sure, popped up again about 10-15 miles later.

So, is there any way that anybody knows of for me to test that I got the 4 wires into the plug correctly?
I know there's two wires for the heater, and then a voltage applied to a third wire, resistance created by the reading of the O2 sensor, and then the fourth wire going back to the ECU.

As I'm typing this I came up with an idea, not sure if the wires are long enough, but I could possibly switch the wires between the front downstream O2 and the rear downstream O2, reset the code, and the new code it would throw might help me figure out whether it's the new O2 sensor not working, or the new plug I connected having issues. I'll have to take a look in the morning to see if the cables might reach. I suppose I could even use some jumper wires for extensions for long enough to throw a code.

Any other ideas or knowledge on how to diagnose this problem further?

Right now I've still got the TJ to get me around, so I'm planning on driving it until I get these codes cleared up just so I can try to get in under the 80k warranty.

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