The gauge in my 98 GrandPrix 3800 reads half of what it should also. I replaced the 3 wire coolant temp sender, and thermostat, with no change, except a $50 lighter wallet. My code reader shows that the ECU says the temp is normal operating temp also. I think there is an issue with the gauge cluster but I dont know. Maybe there is a resistor in line or something. Not a clue. I too would like to know what the issue is.


Jay