During this time period, GM and Chrysler products, which I'm very familiar with, did things the same way. On the Chryslers, the gauge sending unit has only a single wire. The engine computer's sensor has two wires.
Unplug the sensor you replaced while the engine is running. If the Check Engine light turns on, that's the computer's sensor. If the gauge drops to "cold", it's for the gauge. If both things happen, then indeed the gauge would appear to be getting its information from the engine computer, possibly by way of the body computer.
Again, on Chryslers with electric fans, unplugging the computer's sensor will trigger the computer to turn on the radiator fan and put the ignition system into base timing mode. It does that because it knows it can't believe the sensor information and it will not know if the engine is overheating. Running the fan is a precaution. It will turn the fan off when the sensor is plugged back in. Im not sure if GMs turn the fan on, but it will turn the Check Engine light on.
Caradiodoc
Friday, February 26th, 2010 AT 12:45 AM
