Medium and Heavy Trucks
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Thanks for asking your question. I will try and help you out.
The ECM has a coolant temp sensor located in the front of the thermostat housing. This is how the ECM reads engine coolant temperature.
Please reply back if you need more help or have more questions. I am happy to assist.
Yes it will continue to show a reading. That is called a default reading. When unplugged the coolant temp will read 194 degrees F, the ECM will also cut the fan on.
Does it change up and down with it unplugged? or when plugged up?
Thanks for the information.
It sounds like you have a problem in the wiring harness or ECM. I would try pulling the coolant wires from the ECM. This would be pins 32 and 18 in the 70 pin connector. I have seen faulty wiring harness do this before on 2 wire temp sensors.
Pin 2 is the ground. Pin 1 is the signal wire. If you test the wire it will have 5 volts on it. But the is s simple resister, you most likely have a wire in the harness touching something its not suppose to.
Here is the schematic.