Thread: Cooling troubles on Grand Prix

I have a 2006 GP GT. When the ambient temp is warm and the car is in traffic it will get hot. When the ambient temp is cold the car will not reach operating temperature while driving.

My first instinct was that the thermostat was bad. So I replaced the thermostat and flushed the coolant. This had no effect.

When hot the fans kick on when they are supposed to. The car has a new radiator cap too. No leaks and no issues with pressure testing.

Took to the dealer thinking it was under warranty. They couldn't find anything actually wrong with it because they couldn't diagnose it so my warranty did not pay them I needed to.

Any thoughts or suggestions from previous experiences would be great!

The car has two stage fan control. Possibly there is an issue there. Also, make sure there is coolant in the bottle. If not, it will be slow to warm up. Here is the GM serv manual diagnosis for the fans. Lengthy, but this is what can be checked for the fans. The links will not work, so don't try to click on them.


Did you perform the Diagnostic System Check - Vehicle?
Go to Step 2
Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2

1. <LI type=1>Install a scan tool. <LI type=1>Turn ON the ignition, with the engine OFF.
2. With a scan tool, command the Fans Low Speed ON and OFF.

Do the low speed engine cooling fans turn ON and OFF with each command?
Go to Step 3
Go to Step 4
3

Important:

A 3-second delay occurs before the powertrain control module (PCM) changes the cooling fan speed.

With a scan tool, command the Fans High Speed ON and OFF.
Do the high speed engine cooling fans turn ON and OFF with each command?
Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
Go to Step 12
4

1. Important
   
   Do NOT remove the 20-amp fused jumper wire connected during this step. Use a second 20-amp fused jumper wire while performing the following steps.
   
   <LI type=1>Remove the fan 1 relay.
2. Connect a 20-amp fused jumper between the battery positive switch side voltage circuit and the fan motor supply voltage circuit of the cooling fan 1 relay.

Do both cooling fans operate in low speed?
Go to Step 22
Go to Step 5
5

1. <LI type=1>Disconnect the fan 2 relay.
2. Connect the second 20-amp fused jumper between the cooling fan low reference circuit and the cooling fan motor supply voltage circuit of the fan 2 relay.

Do both cooling fans operate in low speed?
Go to Step 23
Go to Step 6
6
Connect the second 20-amp fused jumper between the battery positive voltage circuit and the cooling fan motor supply voltage circuit of the fan 2 relay.
Does the right cooling fan operate in high speed?
Go to Step 9
Go to Step 7
7

1. <LI type=1>Install the fan 2 relay. <LI type=1>Disconnect the right cooling fan electrical connector.
2. Connect the second 20-amp fused jumper wire from the cooling fan motor supply voltage circuit to the ground circuit of the right cooling fan electrical connector.

Does the left cooling fan operate in high speed?
Go to Step 25
Go to Step 8
8
Connect the second 20-amp fused jumper wire from the cooling fan motor supply voltage circuit of the right cooling fan electrical connector to a good ground.
Does the left cooling fan operate in high speed?
Go to Step 29
Go to Step 30
9

1. <LI type=1>Install the fan 2 relay. <LI type=1>Disconnect the left cooling fan electrical connector.
2. Connect the second 20-amp fused jumper wire from the cooling fan motor supply voltage circuit to the cooling fan low reference circuit of the left cooling fan electrical connector.

Does the right cooling fan operate in high speed?
Go to Step 26
Go to Step 10
10
Connect the second 20-amp fused jumper wire from the coil side battery positive voltage circuit to the cooling fan low reference circuit of the cooling fan electrical connector.
Does the right cooling fan operate in high speed?
Go to Step 11
Go to Step 31
11
Probe the battery positive voltage circuit on the switch side of the fan 1 relay with a test lamp that is connected to a good ground.
Does the test lamp illuminate?
Go to Step 27
Go to Step 32
12
Is the right cooling fan operating properly in high speed?
Go to Step 19
Go to Step 13
13

1. <LI type=1>Turn OFF the ignition. <LI type=1>Disconnect the fan 3 relay. <LI type=1>Turn ON the ignition, with the engine OFF. <LI type=1>Connect a test lamp between the high speed cooling fan relay control circuit and the battery positive voltage circuit on the coil side of the fan 3 relay.
2. With a scan tool command the High Speed Fans ON and OFF.

Does the test lamp turn ON and OFF with each command?
Go to Step 15
Go to Step 14
14
Probe the battery positive voltage circuit on the coil side of the fan 3 relay with a test lamp that is connected to a good ground.
Does the test lamp illuminate?
Go to Step 34
Go to Step 33
15
Install a 20-amp fused jumper between the battery positive voltage circuit on the switch side of the fan 3 relay and the cooling fan motor supply voltage circuit.
Does the right cooling fan operate in high speed?
Go to Step 24
Go to Step 16
16
Probe the battery positive voltage circuit on the switch side of the fan 3 relay with a test lamp connected to a good ground.
Does the test lamp illuminate?
Go to Step 17
Go to Step 33
17

1. <LI type=1>With the 20-amp fused jumper still installed. <LI type=1>Disconnect the right cooling fan electrical connector.
2. Connect a test lamp from the cooling fan motor supply voltage circuit to the ground circuit of the right cooling fan electrical connector.

Does the test lamp illuminate?
Go to Step 25
Go to Step 18
18
Probe the cooling fan motor supply voltage circuit of the right cooling fan electrical connector with a test lamp that is connected to a good ground.
Does the test lamp illuminate?
Go to Step 29
Go to Step 30
19

1. <LI type=1>Turn OFF the ignition. <LI type=1>Disconnect the fan 2 relay. <LI type=1>Turn ON the ignition, with the engine OFF. <LI type=1>Connect a 20-amp fused jumper between the cooling fan low reference circuit and the ground circuit of the fan 2 relay.
2. With a scan tool command the Fans High Speed ON and OFF.

Does the left cooling fan operate in high speed?
Go to Step 20
Go to Step 28
20

1. <LI type=1>Connect a test lamp between the high speed cooling fan relay control circuit of the fan 2 relay and the battery positive voltage circuit of the fan 2 relay.
2. With a scan tool command the Fans High Speed ON and OFF.

Does the test lamp turn ON and OFF with each command?
Go to Step 23
Go to Step 21
21
Probe the battery positive voltage circuit of the fan 2 relay with a test lamp that is connected to a good ground.
Does the test lamp illuminate?
Go to Step 34
Go to Step 33
22
Inspect for poor connections at the fan 1 relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 40
Go to Step 35
23
Inspect for poor connections at the fan 2 relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 40
Go to Step 36
24
Inspect for poor connections at the fan 3 relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 40
Go to Step 37
25
Inspect for poor connections at the harness connector of the right cooling fan. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 40
Go to Step 38
26
Inspect for poor connections at the harness connector of the left cooling fan. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 40
Go to Step 39
27
Repair the left cooling fan motor supply voltage circuit for an open. Refer to Wiring Repairs in Wiring Systems.
Is the repair complete?
Go to Step 40
--
28
Repair the left cooling fan ground circuit for an open. Refer to Wiring Repairs in Wiring Systems.
Is the repair complete?
Go to Step 40
--
29
Repair the right cooling fan ground circuit for an open. Refer to Wiring Repairs in Wiring Systems.
Is the repair complete?
Go to Step 40
--
30
Repair the right cooling fan motor supply voltage circuit for an open. Refer to Wiring Repairs in Wiring Systems.
Is the repair complete?
Go to Step 40
--
31
Repair the left cooling fan low reference circuit for a short to ground or an open. Refer to Wiring Repairs in Wiring Systems.
Is the repair complete?
Go to Step 40
--
32
Repair the fan 1 relay battery positive voltage circuit for an open.
Is the repair complete?
Go to Step 40
--
33
Repair the battery positive voltage circuit for the fan 2 relay and fan 3 relay for an open.
Is the repair complete?
Go to Step 40
--
34
Repair the high speed cooling fan relay control circuit for an open.
Is the repair complete?
Go to Step 40
--
35
Replace the fan 1 relay.
Is the repair complete?
Go to Step 40
--
36
Replace the fan 2 relay.
Is the repair complete?
Go to Step 40
--
37
Replace the fan 3 relay.
Is the repair complete?
Go to Step 40
--
38
Replace the right cooling fan. Refer to Cooling Fan Motor Replacement - Electric .
Is the repair complete?
Go to Step 40
--
39
Replace the left cooling fan. Refer to Cooling Fan Motor Replacement - Electric .
Is the repair complete?
Go to Step 40
--
40
Operate the system in order to verify the repair.
Did you correct the condition?

Thanks. No joke about that being lengthy. I will need to set aside some time to go through that on a weekend.

I should add that the car was perfect until one day a couple months ago this all started. I can pinpoint the date. I had driven the car for 95 miles in 95 degree heat with the air going full. I had the cruise set at about 82. When I got into traffic the gage was very quick to move up. The car had burned all the antifreeze out of the reservoir during that trip. It had just been serviced 2 days earlier and checked at that time.

The system has been bled by me and the dealership for a total of about 6 times. There is no air left in it to my knowledge.

I thought that would be the problem too after the thermostat first being changed.

Is there a supercharger on it? I have a compg and it runs very hot. Not enough cooling in traffic with the air on, however it does ot over heat. i make sure the over flow bottle is full on trips.

Join Date11-03-2009
Last Activity
09-07-2011

Don't think the OP is going to answer, especially from a 3 year old post.

BTW, these cars run hot naturally. If it's not overheating then its fine.