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2003 Pontiac Grand Prix Cooling fans

Tiny
SCOTTWOLLESEN
  • MEMBER
  • 2003 PONTIAC GRAND PRIX
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 70,000 MILES
I read through your FAQ's and believe I have narrowed the solution to my problem down to the coolant temp sensor but one thing leaves me unsure.
Niether of the cooling fans run under normal operation. I turn the A/C on and they kick on and off as they should so that tells me the relay and the motors are good. What has me unsure about the coolant sensor being the culprit is the fact the water temp gauge seems to be acurate. Is there a seperate sending unit for the water temp gauge? Or could the indication portion of the sensor still be functioning yet not sending a signal to the relay to kick the fans on?
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Sunday, March 30th, 2008 AT 7:39 PM

6 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
The coolant temperature sensor feeds the PCM the engine temperature at which time the PCM energizes the fan relay-see below


https://www.2carpros.com/forum/automotive_pictures/12900_tps_1.jpg




https://www.2carpros.com/forum/automotive_pictures/12900_tps2_1.jpg




https://www.2carpros.com/forum/automotive_pictures/12900_tps3_1.jpg

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Sunday, March 30th, 2008 AT 8:12 PM
Tiny
SCOTTWOLLESEN
  • MEMBER
  • 11 POSTS
I checked today and niether Chiltons or Hayes makes a manual for my car so I hope you don't mind a couple more questions. I'm not really sure where to start. I found the relays and the PCM. I think reading out the input voltages to those mini relays is beyond my capability and my mini electrical tester.

From what you sent me it seems like I need to replace the PCM. Do you agree?
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Monday, March 31st, 2008 AT 12:07 AM
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Have you replaced or tested the coolant temperature sensor?

If the wires are good/fan motor good/relays all you got left is the relay control of the computer
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Monday, March 31st, 2008 AT 4:53 AM
Tiny
SCOTTWOLLESEN
  • MEMBER
  • 11 POSTS
No I havn't replaced anything yet. I thought the problem might be the temp sensor but I didn't think it could be bad yet still send acurate information to the gauge in the dash.
All my tinkering years I have focused on mechanical portions of the car and avoided electrical stuff. Thats biting me in the ass now. I find myself throwing parts at it rather than troubleshooting.
I am going to start by replacing the coolant sensot today. I sure appreciate your help!
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Monday, March 31st, 2008 AT 10:27 AM
Tiny
SCOTTWOLLESEN
  • MEMBER
  • 11 POSTS
Changed the coolant sensor today and the cooling fans kicked on at about 200 degrees and brought it right back down to 160. Piece of cake. Thanks for your help.
One thing that might be note worthy is I discovered the part number for the sensor on this car is miss marked in the Delphi cataloge. The part Delphi calls for has two terminals and the correct on has three. We checked the picture in the book to make sure it was a cataloge issue and not miss boxed. NAPA looked it up in another brand (Echlin) and they list the correct part.
Again, thanks for your help.
Scott
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Monday, March 31st, 2008 AT 6:49 PM
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Subject: Thanks
Tried to give you some feedback points but since this only my frst time on the site I only have 0.3 points and it wouldn't let me give you those. Won;t let me comment without giving points either.
This service is huge for military guys like me that can't afford $80 an hour for labor at the garage. Very pleased with this site and your personal attention. I'm sure I will have future needs and maybe will rack up some points to give.
Thanks for all your help.
Scott

You're very welcome Freedom Fighter and I appreciate your service to this country its your turn lol spread the word around about us that's good enough with me.

Vietnam Vet
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Monday, March 31st, 2008 AT 7:16 PM

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