Anybody Know Anything About Grand Prix???

[Harley]

Got a 99 GT 3.8 with some cooling system issues that have me stumped. Gauge reads high even though engine temp is normal and the fans don't come on. hot wired the fans and they work fine, checked the fan fuses and replaced the two relays. Also replaced the coolant temp switch, new thermostat and fresh coolant. Is there something I'm missing or could the ECM be faulty....?

[Mountain Dude]

There are usually two coolant sensors. 1 for the computer and 1 for the gauge.

[Harley]

yeah some do but in this case seems to be only the one. Its a 3 wire that is under the thermostat housing. Every place I called only lists one.

[Mountain Dude]

OK, sorry I couldn't help.

[knever3]

You could run the car unplug the temp sensor get an OHM meter measure the resistance change and convert it to degrees most likely in the electrical service manual. Is the car getting heat? How do you know the engine temp is normal if the gauge reads high? Take it to a shop where they have a snap on scanner that reads real time. That will show your exact engine temp and see if the car is going into closed loop, meaning that the ecu can see that the engine is up to temp and the trans can shift into OD and idle down, closing the EGR valve. I can go on and on guessing but a scanner will tell you everything.

[Harley]

Checked the temp off the thermostat housing with an infrared thermometer. yeah, heat blows just fine.