Missing O2 sensor harness
 

Hello to all. first I have a 1991 XJ 4.0 HO 5 speed made for export, and am living and working overseas ( middle East ) I am getting it all ready to ship the jeep home and I noticed my O2 sensor is NOT in place in my exhaust pipe. there is a plug in the hole where the sensor should be. I want to install a sensor, getting the sensor is no problem BUT I can't locate the connector plug it is supposed to connect to. also, is it a 3 or 4 pin connector ? I see different ones for sale at Rockauto.:dunno: I sort of know where it should be, but I can't locate it. can someone please tell me where I should be looking ? I have looked on line for diagrams and it says it should be running from the harness up by the temp switch in the Thermostat housing, but for the life of me I can not locate it. could this have been removed because it is made for Export ? or is it cut off somewhere and just taped up ? I don't get any CEL or anything so if it was removed, any one have an idea as to how I would rewire it back into the system ? I sure hope to hear from someone soon. thanks in advance.

Being where it was destined to go, It was made without it since that country doesn't use it. No cat either. It just needs the one O2 to get mixture right.

well it has the cat on it, and i was wondering if i can wire in the 02 sensor? I would think the computer needs to know what the 02 is so it can make adjustments to the mixture.....wonder how it was setup to not have an 02 in it. i have a different ECU than the one it came with and it never says anything about 02 or CEL....so some how the ECU thinks it is connected to an 02 sensor....right ? help....

There should be one o2 sensor by the engine for mixture and such.

Take some pics of your exhaust setup. Non California jeeps had just 2 o2 sensors and the single cat down to the rear cat. California compliance jeeps had 4 o2s and dual cats. And which o2 don't you see. Top or bottom.

there is only a place for the up stream sensor, near the exhaust manifold, nothing any where else in the exhaust system. I am mostly concerned that I can't find or don't have the harness for the up stream sensor. I can't find it any where. I might have to wire it in, but am not sure how to do it. Also IF the harness was removed because this is an export model, how is the ECU not confused and how does it know how to adjust the mixture ? thanks for all the good comments.....

Only one above you say. And there's only one cat too.

If no one give you the answer of where that harness is exactly by the time I get home from work tonight, ill snap a pic.

If you check the engine bay, do you see any empty large grey connectors around the passenger side engine bay. Iirc there's 2 over there that snap onto the bracket of the engine a long with some thing else, forgot what. And on the drivers side towards the rear from looking under you should see one.

The parts manual shows an export * conversion package.

* Conversion Pkg. Leaded Fuel EXPORT
4638 047 1 1991-92

Cat converter____

4.0L Engine
5201 8104 1 Federal 1991-92
5201 8128 1 Federal 1993
5201 8103 1 California 1991-92
5201 8141 1 California - Auto Trans. 1993
5201 8128 1 California - Manual Trans. 1993

OXYGEN SENSOR ***
5600 5925 1 YJXJMJ 6 Cyl. w/18" Pigtail
5602 6827 1 ZJ 6 Cyl. w/22" Pigtail (Oxygen Sensor-J1930)
5300 7638 4-Cyl., w/4-Hole Zirconium
5600 5925 318 Eng., 1992-93
- 5601 7862 1 ZJ PLUG, Oxygen Sensor, w/Leaded Fuel
- 4625 095 1 Y1XJMJ JUMPER WIRE, Oxygen Sensor ***

Some countries used or still use a resonator instead of a cat converter.
14 5200 3940 1 RESONATOR, Leaded Fuel - KDX ***
X1=Cherokee, Briarwood

p/n's Europe wiring is the same as a diesel.

5601 7406 XJ,MJ WIRING, Alternator/Battery, 6 Cyl., 1991
5601 7610 1 MJ,XJ 1992
5601 7778 1 MJ,XJ 1993
5601 8315 1 XJU 1993

5600 4298 1 XJ 1991, Diesel Eng., EUROPE
5601 8028 1 XJ 1992-93, Diesel Eng., EUROPE

I'm uncertain about the part of the wiring harness for the PCM and oxygen sensors. I don't see any specific wiring and connectors for the o2 sensors. Jeeps usually have an engine wiring harness connected to other harnesses installed inside.

* Locate your PCM (ECU) Chrysler OEM part number, then cross-reference to the type of PCM module you have installed.

Different modules were used for Europe, leaded fuels, etc.

1991, w/o RFI (6-Cyl. Eng., Man. Trans.) XJMJX1

(Leaded Fuel) (6-Cyl. Eng., Man. Trans.) XJMJX1

1992, w/o RFI, EUROPE (6-Cyl. Eng., Man. Trans.)

http://www.moparpartsgiant.com/parts...ule-mj-xj.html

http://www.moparpartsgiant.com/parts...briarwood.html

Problem solved
 

well I removed the air box and really dug into the lower part of the engine, I found an old dirty harness that ran down behind the power steering pump to a bracket, and it had a 4 pin connector on the end of the harness. it has to be the connector for the O2 sensor. it has a plug pluged into it with a jumper wire on it, I guess this is how the computer thinks the O2 sensor it present. I have already ordered a O2 sensor from Rockauto, and when it gets here I will install it, so maybe now the computer can adjust the mixture and maybe this will also improve my mileage. thanks for all the help and suggestions in helping me to solve this crazy issue.

thanks again

I just realized I never took those pictures. I'll snap them later too just for reference. Usually brain shuts down when I leave work

Glad you found the connector.

There may be a difference if the PCM is programed for leaded vs unleaded fuel

The heater wires also need to be enabled and functioning,
____

Here's a European 1991 PCM, description shows some are designed for use with leaded gas.

R4762626 SINGLE BOARD ENGINE CONTROL MODULE . 4-Cyl. Eng., Man. Trans., 6-Cyl. Eng., Man. Trans., 6-Cyl., Eng., Auto. Trans., NOTE: RFI=RADIO NOISE SUPPRESION Sales Code for RFI is JLW. (Leaded Fuel), 1991, w/o RFI, 1992, w/o RFI.
SINGLE BOARD ENGINE CONTROL MODULE . 6-Cyl. Eng., Man. Trans.. (Leaded Fuel). . Required: 01

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Here we go. These are for the two upper o2 on a Cali emmision 01 XJ. Didn't get a chance to crawl under for the lower ones.

thanks guys for all the input.

All done and Thanks
 

WEll I am all done with the O2 sensor problem, I got a new NTK sensor from rock auto installed it and plunged it into the harness and all is good, I have noticed an increase in my MPG and it just seems to run better. thanks for all the input and help and this is just one more step towards getting her ready to send back home. thanks

Glad all is well. Thanks for the update. Were here when ever you need us