temp gauge malfunction

**Mastiff** · 07-21-2011

OK heres the problem the temp gauge goes full upper scale with car at idel.

The car

2002 grand prix 3.8 S/C anniversary edition sedan

The problem

Temp gauge on cluster pegs out @ 260 + with in 60 seconds of operation
slower with engine off ( takes a few minutes but will max out with cold eng)

The facts

1. LIM just replcaced

2. coolant system bled and no air in system

3 replaced coolant temp sender twice problem still present

4. with scan tool connected temp is around 216 at idle fans on with A/C ( OKC is hot as ever this summer so i don't think this is all that bad)

5. car runs fine no leaks and has a good idle

6. looked over the wire harness and found no obvious evidence of damaged wires.

7. I am about ready to slap a chunk of C4 under the car and see how many pieces are left after detonation..

any input would be appreciated thank you.

**BillBoost37** · 07-21-2011

The temp sensor has two outputs and one input. This means taht one output feeds the cluster and another feeds the pcm. You've done all the right things with checking that the gauge or gauge feed is incorrect and the pcm sees it correctly.

This is sounding like a wire break etc. When the motor heats up the wire expands and pegs high. Try warming up the car and having a friend watch the gauge while you wiggle the wiring harness. Maybe you'll get lucky and it'll be the short leader that goes on to the sender.

**Mastiff** · 07-22-2011

I have done that / looked over the short lead looked old but no real damage... I think this is going to come to getting the pin outs and using a Meg-er to ring out the lines with the components disconnected.

The things I do for roommates... and their non-maintained cars, this car has mega issues electrically.

The DIC / HUD / AC / radio work when they feel like it.... after working on this car I have regained my Happy feeling of joy when I work on a old as hell Boeing, at least they have to be maintained...

thank you for the input !

**Bob Padilla** · 07-22-2011

Originally Posted by Mastiff

I have done that / looked over the short lead looked old but no real damage... I think this is going to come to getting the pin outs and using a Meg-er to ring out the lines with the components disconnected.

The things I do for roommates... and their non-maintained cars, this car has mega issues electrically.

the DIC / HUD / AC / radio work when they feel like it.

thank you for the input !

Iirc there are 2 temp sensors bro just like on most gm cars/trucks ,one for the gauge and one for the pcm.

Did you replace 2 or one?

**Mastiff** · 07-22-2011

one .... located under the thermostat housing.

I have only seen reference to one in this system. one temp sender unit and one low level sender.
If you have any more that I don't know of then I am all ears because I am about sick of this car.
I am so frustrated with it that if it doesn't say Volkswagen or Boeing on the name plate I don't even want to touch it ... in other words I am so out of my comfort zone it isn't even funny.

Thanks

**BillBoost37** · 07-22-2011

Put a stickey note over the gauge. It's optional.

**Mastiff** · 07-22-2011

now that's damn good idea

**tayl5645** · 07-22-2011

Originally Posted by BillBoost37

Put a stickey note over the gauge. It's optional.

Now bill.... I know you wouldnt drive your car like that so should you really suggest it to someone?

**Mastiff** · 07-23-2011

It's all good I realize that he is simply joking.

**jmt455** · 07-24-2011

Originally Posted by Mastiff

...The things I do for roommates... and their non-maintained cars, this car has mega issues electrically.

The DIC / HUD / AC / radio work when they feel like it.... after working on this car I have regained my Happy feeling of joy when I work on a old as hell Boeing, at least they have to be maintained...

thank you for the input !

That DIC/HUD/AC behavior is usually a sign of a bad ignition switch.

Here is a link to a good write-up on diagnosis:Sparky's Answers: 2002 Pontiac Grand Prix Blower Inoperative, Erratic

And here is an excellent "How-To" for ignition switch replacement: Sparky's Answers: 2002 Pontiac Grand Prix, Changing The Ignition Switch

My 2002 GTP was doing all kinds of strange things. I replaced the bad ignition switch and everything worked properly again. I doubt this would have anything to do with the Temp gauge problem in the OP, but it might be the cause of many other electrical issues.

**Mastiff** · 07-25-2011

thank you for the info much obliged

**spyder2001** · 08-21-2011

Just wondering if you found a solution to this problem, i too did the lim gaskets, replaced the temp sender twice and am experiencing the exact same problems. I used an infrared thermometer on the thermostat housing and it'll consistanly stay between 190-200 degrees so i ordered a used instrument cluster thinking maybe the temp guage shorted out but am waiting to receive it yet.