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The evil CHECK ENGINE light

I have a '96 Dodge Dakota SLT, and my mechanic can’t get the check engine light off. Replaced both O2 censors last week, which got the light off for all of 15 miles. He’s checked for loose connections, reset systems, and more. The diagnostic still says the O2 sensors are bad, even though we know that’s not true. I’m thinking I could need a new onboard computer. I’m sure a dealership could tell me for sure, but the truck (198000 mi.) isn’t worth much. I’m afraid by the time they’re done with it, the bill would be more than the truck’s worth. Any suggestions??

Please post the OBD codes that cause the CEL to come on…

Get a new mechanic.

There are no codes that tell you that an O2 sensor is bad. Find out what the specific codes are - they look like “P1234” - and post them here. If your mechanic didn’t write them down many auto parts stores will read them for free.


P0132 O2 Sensor Circuit High Voltage (Bank 1(1) Sensor 1)
P0135 O2 Sensor Heater Circuit (Bank 1(1) Sensor 1)
P0138 O2 Sensor Circuit High Voltage (Bank 1(1) Sensor 2)

If the sensors have been replaced and if these were the initial codes that remain after new sensors, then you’re most likely looking at a wiring problem. Reliable & w/in spec voltage has to get to the sensors and signals from the sensors have to make it back to the PCM. The easiest place to start would be with a wiring diagram to find out what, if any, circuits the front & rear sensors share.