Fault Code 22 Problem & Fix (Sort of)

[HOrnbrod]

Had an interesting electrical problem that was a bit weird so I'm posting it up so no one has the go through the same ordeal. I'd been burning more fuel than usual for the last couple of weeks, and had a sketchy idle. Plugs were due, so I changed them out  - no help. Finally checked for fault codes, and I was getting a code 22, "Coolant sensor or circuit.  Check temp sensor and wiring". The sensor involved that causes this code is the one on the thermostat housing that sends coolant temp data to the ECU. I had a new Mopar sensor, stuck it in, cleared the codes, and drove it for a couple of days with no improvement. Same damn code 22. Pulled the 60-pin ECU connector and checked for continuity from the sensor connector to the ECU and all was well. Then measured the sensor resistance across the sensor pins, connector off, both with a cold engine and then at operating temperature, resistance changed as it should within specs. WTF??

Happened to glance in the 2-wire connector on the sensor harness, and one of the female pins was recessed just a tiny bit more than the other, just enough so that it wasn't making good contact with the sensor male pin. Luckily I had another connector, spliced it in, cleared the codes again, and the problem was gone.

 

Moral: Check the physical connection to the sensor first. If you suspect an air gap problem, replace/repair the sensor connector.

[Ωhm]

Good find. Never underestimate the value of the visual inspection.