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Ron
Ron, ASE Certified Technician
Category: Pontiac
Satisfied Customers: 33468
Experience:  34 years as a Tech
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I have a 2000 Pontiac Grand Prix. I believe that my

Customer Question

I have a 2000 Pontiac Grand Prix. I believe that my thermostat is stuck. When driving the temperature gauge always rises to red line but the temp light never comes in till yesterday. It went way past the top of the thermometer gauge High Point. Then the temp light came on. When idling temperature gage likes to rise to the redline but once I start pushing the gas and moving it drops back down.
Submitted: 3 months ago.
Category: Pontiac
Expert:  Ron replied 3 months ago.

Hello,
My name is ***** ***** I am here to assit you with your question and help you resolve your concern.

Expert:  Ron replied 3 months ago.

Have you checked the coolant level to be sure its full?

Is the cooling fan coming on?

Customer: replied 3 months ago.
The fans don't come on
Expert:  Ron replied 3 months ago.

If the fans are not coming on then that is likely your problem. That would explain why it cools down when you start driving as your pushing air across the radiator. Has the system been scanned to see if there are any fault code setting?

Customer: replied 3 months ago.
No I have no lights on . No check engine or anything.Could it be the whole fan or just a wire or fuse
Expert:  Ron replied 3 months ago.

It could be any of the above. Are you able to do some testing?

Customer: replied 3 months ago.
Not at the moment. They come on when th a/c is turned on. Just don't run while idling
Expert:  Ron replied 3 months ago.

That means the fans are not the problem, one thing you can try is to disconnect the engine coolant temp sensor with the engine running and see if the fan comes on. Check this and let me know.

Customer: replied 3 months ago.
I don't know where that's located
Expert:  Ron replied 3 months ago.

Its in the engine just below the thermostat housing . See the diagram in the link below for location.

https://dl.dropboxusercontent.com/u/104923897/ECT%20Sept%209.pdf

Customer: replied 3 months ago.
Still can't find it.
Expert:  Ron replied 3 months ago.

Are you able to see the thermostat housing? It right below it.

Customer: replied 3 months ago.
No clue. I can't tell from the diagram. I'm not real car savy once I learn I can do it but his one thing I've never done
Expert:  Ron replied 3 months ago.

This is the 3.8 engine right?

Customer: replied 3 months ago.
It's says 3100 Sfi on the engine
Expert:  Ron replied 3 months ago.

Okay thats a different location, on the 3.1 its on the block just below the fuel pressure regulator located on the fuel rail. See this link.

https://dl.dropboxusercontent.com/u/104923897/ECT%20Sept%209.pdf

Customer: replied 3 months ago.
I've got the sensor unplugged and the fans did come on
Expert:  Ron replied 3 months ago.

The fan should have come on with the sensor unplugged. That usually means the PCM (computer) is not seeing the signal from the ECT. If your sure your fans run with the AC on and the cooling system is full then that usually means the PCM is at fault.

Customer: replied 3 months ago.
How do I fix that
Expert:  Ron replied 3 months ago.

You would need to replace the PCM and programming would need to be done. I think before you jump to this step you would need to have some hands on professional testing done to be sure the PCM is at fault.

Customer: replied 3 months ago.
this is something I can't do myself. What's the average cost with this?
Expert:  Ron replied 3 months ago.

This is not something your likely to do with out a good scan tool. Most shops are going to charge about 1.5 hours in labor to diagnose this for you.

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