98 Cherokee Sport O2 issue - JeepForum.com
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post #1 of 11 Old 06-10-2021, 03:48 PM Thread Starter
RobinC
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98 Cherokee Sport O2 issue

My 98 Cherokee Sport 4.0 threw a code about a month ago for the upstream O2 sensor, so I bought the part, and my son installed it (yes, he was trained as a mechanic). After one day of driving, the check engine light came on again, this time indicating both the O2 sensors were the problem. I bought the other sensor, had it installed, and the same exact thing happened after one day of driving. Not only is the light on again after clearing the codes, but the engine runs rough in low gear and idle, but surges, trying to push me into the guy in front of me at the light. I cleaned the throttle body and TPS yesterday (lots of carbon) and cleared the code again, cleaned some ground wires, and the light is back on again. About to take it to check the codes (again), but I'm almost afraid to drive it. Had another mechanic take a look at it the other day, and he thought the MAP sensor could be the problem. If any of you gentlemen/women have any insights or suggestions, I would love to hear it! Thanks in advance...

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post #2 of 11 Old 06-10-2021, 04:14 PM
CJ7-Tim
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What brand of O2 sensors were installed ?

The Check Engine Light trouble codes are a guide to help with diagnostics, O2 sensor codes can also indicate excess fuel from faulty fuel injectors, internal coolant leaks, blown O2 sensor fuses, and O2 sensor wire harness or wire plug issues.

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not to overthrow the Constitution but to overthrow the men who would pervert the Constitution” Abraham Lincoln, 1859.
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post #3 of 11 Old 06-11-2021, 08:46 AM Thread Starter
RobinC
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Thank you for the info. I will check the fuses next, then take a look at the plugs and wiring harness. I appreciate your time.
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post #4 of 11 Old 06-11-2021, 11:13 AM
CJ7-Tim
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What brand of O2 sensors were installed ? The Jeep 4.0 L is very particular about the brand of O2 sensors installed. Numerous 4x4 forum threads detail trouble codes and drivability issues related to generic auto parts store O2 sensors, and BOSCH O2 sensors.

The Jeep 4.0 L runs best with genuine Jeep O2 sensors, or with NTK O2 sensors. Cheap parts are cheap for reason.


Good Luck.

“We the people are the rightful masters of both Congress and the Courts,
not to overthrow the Constitution but to overthrow the men who would pervert the Constitution” Abraham Lincoln, 1859.
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post #5 of 11 Old 06-11-2021, 02:37 PM
jtec
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maybe if you post ALL the codes it would help narrow this down.
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When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #6 of 11 Old 06-12-2021, 09:14 AM Thread Starter
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Both O2 sensors are NTK, so I'm good there. Going to take it somewhere to have the code(s) read again this evening, to see if it's the same as before.
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post #7 of 11 Old 06-13-2021, 12:37 AM
tjwalker
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Agree with Jtec, with any code(s), the devil is in the details.

Post the exact codes here for comment (not just a description of the code).

99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche
Without "data", all you have is an opinion!
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post #8 of 11 Old 06-14-2021, 08:33 AM Thread Starter
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Have been delayed by a broken toe, but hope to get back on my feet today and get the code(s) read. Thanks for your patience.
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post #9 of 11 Old 06-14-2021, 07:54 PM Thread Starter
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Okay....Had the codes read at Autozone and the print-out lists error codes as follows:
P0135 (O2 Heater Circuit Bank 1/Sensor 1)
P0138 (O2 Circuit High Voltage Bank 1/Sensor 2)
P0141 (O2 Heater Circuit Bank1/Sensor 2)
I pulled the plug apart on sensor 1 this evening to look for bent prongs, but it was fine. I DID find the entire wire harness had come un-clipped from wherever it was clipped, and was resting on the front axle, though still connected. Not quite sure where it attaches to, in order to keep it out of the way of moving parts or stray armadillos...haven't put it back to wherever it clips yet....
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post #10 of 11 Old 06-15-2021, 08:06 AM
jtec
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As we suspected the codes are WIRING, how is your electrical trouble shooting skills?

You might need A wiring diagram, DVOM, and trouble trees.

1998 XJ cherokee 4.0L.
Attached Files
File Type: pdf does this help.pdf (699.4 KB, 1 views)

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #11 of 11 Old 06-15-2021, 09:25 AM Thread Starter
RobinC
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Good news. Just checked the wiring harness before I got your last message, and found a possible trouble area that I have now repaired, and found a blown fuse for the O2 sensor, which I happened to have a spare for. Cleared the codes and ran the engine for a few minutes, and no code....but time will tell if that was the only problem. Both O2 sensors that came out were original and burnt toast. Will be back for more advice if the need arises. Thank you ALL so much! XO
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