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Mr Chill 05-02-2012 09:24 AM

A/c leak causes o2 sensor failure
After doing some maintenece and intake cleaning, I took the Jeep for a spirited drive to get the last of the Seafoam smoke out. On my way back the a/c stops working then a few minutes later a check engine light comes on.

So I put it up on ramps and start looking around. First thing I find out of the ordinary is this neon yellow (think highlighter) fluid coming out of what looks like a small drain spout at the base of the passenger side firewall. Its all over, and soaking the lead wire going to the 2/1 o2 sensor. So I take it to O'Reillys and have the codes pulled.. P0175: system too rich, bank 2. P0151: O2 circuit low voltage bank 2 sensor 1. Ok it seems this fluid seeped into the wiring of the o2 and ruined it.

I can only assume this fluid is an a/c system dye or sealant, which means the previous owner was patching a problem. My thought is the evaporator core given the sudden failure and location of the leak. That won't be a fun repair, but I know I can take the dash out without breaking anything.

For the o2, can anyone chime in with the best way to get at it? This is passenger side pre-cat. My o2 sensor socket is a deep well with a slot and even with two swivels I can't get a good angle on it. Better to drop the y-pipe? I don't want to stress the manifold bolts and create another problem. Or give it to an exhaust shop and have them do it while welding a new muffler in (next mod)?

I gotta believe someone here has had to change this sensor. Any advice?

jeepgcoman 05-02-2012 11:09 AM

Re: A/c leak causes o2 sensor failure
The Seafoam could have caused the problem too. It's job is to clean out the combustion tract. Any contamination that it does clean out has to go past the O2's and the cats. Your "spirited" runs could have had adverse effects. The O2's are vented to the atmosphere through the plugs and wire insulation, so this is indeed a possibility that contamination has gotten into the sensor that way. It would be nice if you could get mv readings on all the other O2's also, to see if any others may be contaminated. Keep us posted.

As far as removing the plug/sensor, removing the "Y" pipe is the easiest way to go. Lot fewer cuss words and bashed knuckles.

Mr Chill 05-02-2012 12:05 PM

Re: A/c leak causes o2 sensor failure
Thats true, Seafoam could be a culprit. I am considering replacing all of them if the pipe comes out. The sensors have Denso written on them.. I'll have to see if those are oem and what the best replacements are. I know the 5.7 is supposed to use NGK but I have not seen much posted about o2 sensors for the 4.7.

2005JGC 05-02-2012 04:10 PM

Re: A/c leak causes o2 sensor failure
denso is oem.

the seafoam is likely the cause for your codes, drive the piss out of it, clear the codes and you will likely be good.

the neon yellow stuff is simply dye which is installed during most services or repairs, our pag oil is mixed with dye so when we add any oil we are adding dye. Its not an indication of a stop leak agent.

Mr Chill 05-05-2012 12:51 PM

Re: A/c leak causes o2 sensor failure
It took a couple rounds of clearing the code, but it hasn't come back in the last 75mi.

See I'm used to GM where the light meant failure, not "drive it harder and it'll go away". Lol

Now.. About that evap core. Sigh.

2005JGC 05-05-2012 02:43 PM

Re: A/c leak causes o2 sensor failure
ANY car will have issues when you suck in random chemical "A" into it... WHEN it has issues with it its just a matter of if the issues it causes cause a sensor to deviate from where it should be beyond a set threshold... when the chemical you make it injest causes a sensor to see outside of the threshold you get the CEL... and that can take some good ol' fashion lead foot driving to clean/burn all the crap out scewing the sensor reading and viola.

Mr Chill 05-05-2012 07:31 PM

Re: A/c leak causes o2 sensor failure
Yeah what threw me was that it was just one of the pre-cat sensors that threw a code, and that sensor was also the one soaked in evaporator barf. False cause and effect I guess.

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