05 Grand Prix Temp Gauge

Asked by GuruLDV74 Mar 21, 2019 at 11:23 AM about the 2005 Pontiac Grand Prix Base

Question type: Maintenance & Repair

I have an 05 Pontiac grand prix.  Temp
gauge was randomly dropping off to
nothing while driving.  Had a new
thermostat about 6 months ago, just
changed temperature coolant sensor.  
Works fine for a day or so then
randomly drops off.  When it drops off
if I shut the car off then it usually wont
start again for about 20 mins until the
car cools down again.  Shop is telling
me I need a new PCM module....any
other suggestions?  I was wondering
about changing thermostat again?  
Also blower fan suddenly stopped
blowing heat into the car....still makes
heat as the car warms up it's just that I
cant get it to blow into the car.  Hubby
works out of town and I am trying to fix
this myself so I dont have a HUGE shop
bill....any help greatly appreciated!

1 Answer


If the car is overheating I'd check that the cooling system is actually full and that there is no air trapped in the system. There is a bleeder valve by the thermostat that can be used to release trapped air. It can be tricky to get the air out though. As for the fan, did it gradually quit, first loosing the lower speeds before stopping entirely. If so, its the resistor in the air duct inside the car. Of course in both cases above it could be other things. Spend money on diagnostics first if you have to before you start replacing things. It's unlikely that its the thermostat if you just replaced it.

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