This 2000 Chevrolet cavalier came in with the SES light on and a code P0118 stored for low coolant temperature among other problems. A quick scan found that the coolant temperature was at -40 degrees F. The outside temperature is in the mid 70’s.
I found the coolant temperature sensor broken and the harness connector damaged.
I installed a jumper wire between the two wires to check the wiring and the computer out.
The temperature reading went to 303 F. That told me that the wires and the computer were all okay. If it had changed to anything significantly lower than 300 F I would have had to do some testing on then wires to determine if there was a wiring problem or an internal computer issue.
I removed the old broken sensor and installed the new one.
I spliced in a new harness connector for the coolant temperature sensor.
Applied heat to the heat shrink tubing.
Everything installed and reconnected.
Now I have the correct coolant temperature reading. The engine had been sitting overnight before I got to it.