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Unread 08-11-2011, 10:17 AM   #1
Matt24138
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1993 YJ Wrangler 
 
Join Date: Apr 2010
Location: Bethany Beach, Delaware
Posts: 259
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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Unread 08-11-2011, 10:29 AM   #2
oldtime_ironman
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1991 YJ Wrangler 
 
Join Date: Dec 2010
Location: 14304 Niagara Falls, NY
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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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Unread 08-11-2011, 10:37 AM   #3
Matt24138
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1993 YJ Wrangler 
 
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I have 4 wires
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Unread 08-11-2011, 10:45 AM   #4
oldtime_ironman
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Join Date: Dec 2010
Location: 14304 Niagara Falls, NY
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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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Unread 08-11-2011, 10:51 AM   #5
Matt24138
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Location: Bethany Beach, Delaware
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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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Unread 08-11-2011, 10:52 AM   #6
Que89YJ
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1989 YJ Wrangler 
 
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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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Unread 08-11-2011, 11:40 AM   #7
Matt24138
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1993 YJ Wrangler 
 
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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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Unread 08-11-2011, 12:29 PM   #8
Que89YJ
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1989 YJ Wrangler 
 
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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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Unread 08-11-2011, 12:38 PM   #9
Matt24138
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I will check it out.
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Unread 08-11-2011, 12:42 PM   #10
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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Unread 08-11-2011, 12:49 PM   #11
Que89YJ
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1989 YJ Wrangler 
 
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Location: Detroit, Michigan
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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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