nik1093

I have a 94 Cherokee, 4.0, AW4
OK this check engine light started coming on after I replaced the transmission in October. I just recently got it read and it came up with 3 codes. o2 sensor short to voltage, o2 sensor stuck at half lift (or something like that), and another pertaining to the o2 sensor. I have been looking for any loose wires or nips in wires that could be causing the short but nothing seems like it would be a problem. I got the wiring diagram and found out what else was on the circuit. It was most of the other sensors so I started unplugging sensors to see if my voltage would go back to normal. It did after unplugging the thermostat housing sensor. What is causing this? I cannot figure it out and I know my gas mileage is suffering because of it. Let me know if you need any more information. Thanks in advance for the help.

DFlintstone

The wires to both O2 sensor heaters both carry a bit of current, (as opposed to just a signal). Because of where they end up there is always a chance of shorting on the hot exhaust pipe. Also the connectors need to pass that current. In one thread I guy had a problem with the wire to the rear shorting. I think 96+(OBD II), has a dedicated relay, (or relays) and fuses just for that. Not sure about yours. Any relay you can reach, you can wire-brush the blades, spray out the socket with electrical cleaner, and plug back with dielectric grease. I think you are going to want to see both power and ground at the sensor, (and the third caries the info). This for a Renix this is interesting. I would guess the newer are similar. http://www.naxja.org/forum/showthrea...ht=sensor+test

If you post your exact codes there may be guys here who can help.

nik1093

wow actually that helped a lot. he has the HO testing on the next post. I had been looking all over and never stumbled upon this. thanks man. ill be checking it out as soon as the snow stops

DFlintstone

Great! Let us know how it turns out. There are endless, endless threads. (and posting the exact codes won't hurt).

Also was thinking maybe those wires to the rear O2 got "perturbed" in the trany swap.

nik1093

ok well it was a little different than the par but I checked in my haines manual and there was a procedure to check the oxygen sensor. it checked out fine. side from receiving extra voltage. but I checked the temp sensor and the reappearance was way high at operating temp. manual says it's suppose to be under 1000 ohms but it's at about 2000. going to get a new temp sensor and see what comes of it. I'll let you know

nik1093

well. that looks like the solution. I replaced the temp sensor yesterday and the cel has yet to show it's ugly head. thanks for the help. this has been annoying me for so long and to think it was just something so simple

DFlintstone

???Glad you got it? Not sure exactly what you did, (or what your codes where),
Are you saying the light went off when you unplugged it? Anyway . well done. Wonder if you will see a mileage improvement, and thanks for getting back.