02 sensor wire harness? - JeepForum.com

 
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post #1 of 11 Old 08-11-2011, 10:17 AM Thread Starter
Matt24138
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02 sensor wire harness?

Ok I replaced my 02 finally passed emissions. Now my problem is it runs like crap until it warms up. I have reset the ECM 6 times. I had a broken wire on the harness that I repaired with solder and a shrink tube. My understanding is the 02 has a heating element that kicks in until operating temp. Anyone know which wire this is. I checked Haynes with no luck. I assume the broken wire was to the element causing my cold running issue and I need to repair my repair maybe cut it back further for a cleaner connection.

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post #2 of 11 Old 08-11-2011, 10:29 AM
oldtime_ironman
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My haynes manual shows the gray and yellow wires are for the heater, and a black wire up the middle is for the actual sensor (2.5L, the 4.o similar)
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post #3 of 11 Old 08-11-2011, 10:37 AM Thread Starter
Matt24138
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I have 4 wires
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post #4 of 11 Old 08-11-2011, 10:45 AM
oldtime_ironman
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Quote:
Originally Posted by Matt24138 View Post
I have 4 wires
My mistake - I dug out the 4.0 diagram. It seems the sense wires on the 4.0 are on pins 1 and 2 in the connector. They should be a gray, and a brown/red. The heater wires therefore would be on pins 3 and 4 in the connector. It says those are black and dark green/black.

The sense wires go directly to the ECU. The heater wires go to the ASD relay and a big junction splice.

Last edited by oldtime_ironman; 08-11-2011 at 10:48 AM. Reason: details
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post #5 of 11 Old 08-11-2011, 10:51 AM Thread Starter
Matt24138
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Ok thanks so much! Now I can figure out my rough start up issue. I am 99% it's the heater not working.
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post #6 of 11 Old 08-11-2011, 10:52 AM
Que89YJ
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If its running like crap until it warms up its probably not your O2 sensor. It doesnt start to get used until its warmed up and in closed loop. Since its starting out bad cold I would check the engine temp sensor.
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post #7 of 11 Old 08-11-2011, 11:40 AM Thread Starter
Matt24138
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It all started when I replaced it. From what I can gather the heating element tells the ECM to use a pre programmed map until it is at temp. If I unplug the 02 the issue stops. So I think with the wire not having a good connection it is telling the ECM that it is heated so it is trying to run the air/fuel mix as if it was warm.
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post #8 of 11 Old 08-11-2011, 12:29 PM
Que89YJ
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It will not read the O2 sensor until the engine is warm enough to go into closed loop. Try this senario, the temp sensor is telling the ecm to read the O2 sensor when the engine isn't warm enough so disconnecting the O2 sensor forces it into a default cailbration. Check the temp sensor.
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post #9 of 11 Old 08-11-2011, 12:38 PM Thread Starter
Matt24138
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I will check it out.
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post #10 of 11 Old 08-11-2011, 12:42 PM Thread Starter
Matt24138
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Any tips for diagnosing it? I know my temp gauge reads correctly. Is it something I can clean?
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post #11 of 11 Old 08-11-2011, 12:49 PM
Que89YJ
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Its a different temp sensor. Our Jeeps have 2. 1 for the guage on the rear and the one for the engine in the front by the thermostat housing.
Here is the resistance readings to check it.

http://www.jeepforum.com/forum/f12/u...38/index2.html
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