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Old 09-22-2012, 09:45 PM   #1
Join Date: Feb 2011
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Check engine light (oxygen sensor) comes on and off

My check engine light is on and its for the upstream Oxygen sensor. I disconnected the battery and it went away, but came back. it then went off again on its own, came back on, the went off. all after several cycles.

This occurred just after i fixed my emissions purge valve circuit. the check engine lite had been on for 2 years. it would not reset. i finally got into the wiring and found a couple breaks (mice) in the wires. fixed them and it went off immediately. it then came back on again after a few cycles. thats when i put the code reader on and found it was the oxygen sensor. the on board diag shows as a 12.

im wondering if now that the purge valve is working if somehow the build up of fumes in the charcoal canister are causing the sensor to trigger the check engine lite.

Any thoughts? my baby is due for inspection and i dont want to take it in and have the darn light come on. in part of pa where they require emissions testing and sticker. if the light comes on, its a no go.

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Old 09-23-2012, 04:29 PM   #2
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Location: Des Moines, Iowa
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I think it's probably just a bad O2 sensor. They live a hard life. I just found out myself on this forum they are all different part numbers and plug-ins and that the so called "universal" ones don't work. Jeep computer doesn't like Bosch, either, I'm told. Make sure you replace the right one with the right part number. I put an NTK brand and haven't thrown a code yet since.
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'02 Sport, soft top, 6 cylinder
5 speed manual, 4" lift, 33.5" tires
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check engine light , oxygen sensor

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