Grand Prix Coolant Temp Sensor Location

Hello, I have a 2000 Grand Prix with the 3.1 in it. The temp gauge isn't working and the cooling fans will not come on. I was told that there is more then one sensor and I'm having trouble with the location. There is only one I see which is right at the side of the thermostat housing and is a three probe plug in.

I was always under the conclusion that it only had one or two wires. Maybe it is different on these newer models?


Answer: Yes, the 3.1L V6 has only 1 sensor. This has 3 wires because it is used by the PCM for fan to prevent overheating, and the dash cluster for temp. gauge. Dark green wire is for the gauge, the other 2 are for the PCM. If the sensor is replaced and these gauge and fans still do not work, i would suspect a wiring problem.

Temperature Gauge Went Into Red

1999 Pontiac Grand Prix SE.
Engine Size : 3.1
Question: On the way to college, my temp gauge flew up into the red. 2 minutes later I parked the car, opened the hood. I heard hissing and steam/smoke coming from somewhere just under the belts. I turned it off and got it towed when the day is done. With a light I could see that maybe the leak is coming from behind one of the spinning things, or one of them that does not spin. Could this be water pump? I'm thinking steam/smoke would be my water pump or water pump seal went. Any help would be appreciated.

Answer: Yes, this does sound like the water pump. The item you are describing is the water pump pulley. It is the pulley under the black plastic belt cover on the front of the engine toward the radiator Many times the belt diagram is on that piece of plastic.

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  • Guest - Mary watts

    I have a 2003 Grand Prix 3100 engine. I am stumped! Replaced water pump gasket, thermostat, and temp sensor. Still shows it's overheating! What's wrong. Really appreciate some help!

  • Guest - tim

    In reply to: Guest - Mary watts

    Your engine may have 2 coolant temperature sensors- one for the computer, one for the gauge. One is on the drivers side back of the rear cylinder head, the other is under the thermostat housing.

  • Guest - will

    I also have a 1999 Pontiac Grand Prix SE.. I changed my temperature sensor and it peaked to hot on start up.. I was told I have to let it reset so I disconnected the battery over night... I got up this morning and connected it back it read fine.. I came home from work to see if it will peak again and as I thought it did... I am clueless of what else I have to do any help would be great.. I have changed my t stat to a fail safe I also changed intake manifold due to it over heating... I have no mixture of coolant and oil so I know its not my head gasket and I also get heat... Fans work but I don't think they are spinning fast enough.. But any help would be great.. Thanks

  • Guest - patty

    I need to know were the second sensor is at on my 95 pontiac grand prix se. I replaced the water pump, thermostat and sensor by the thermostat but can not find the second one.The thermo gauge still is going crazy

  • Guest - Bill

    In reply to: Guest - patty

    The other coolant temperature sensor is located on the back of the rear cylinder head toward the drivers side. It is a 1 wire sensor.