GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: Engine Cooling Schematics

Connector End View Reference: Cooling System Connector End Views

DEFINITION: One or both cooling fan motors are inoperative in either high, low, or both speeds.

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

Test the cool fan LOW, cool fan HIGH and cool fan S/P relay control circuits for an open.

Did you find and correct the condition?

Go to Step 29

Go to Step 3

3

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. 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 4

Go to Step 5

4

Important:: A 3 second delay occurs before the 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

5

    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.

  1. Disconnect the cooling fan LOW relay.
  2. Connect the first 20-amp fused jumper between the battery positive voltage circuit of the cooling fan LOW relay and the cooling fan motor supply voltage circuit of the cooling fan LOW relay.

Do both cooling fans operate in low speed?

Go to Step 14

Go to Step 6

6

Important: The S/P relay is located under the front bumper on the drivers side of the vehicle.

  1. Disconnect the cooling fan S/P relay.
  2. Connect the second 20-amp fused jumper between the left cooling fan motor low reference circuit of the cooling fan HIGH relay and the right cooling fan motor supply voltage circuit of the cooling fan HIGH relay.

Do both cooling fans operate in low speed?

Go to Step 15

Go to Step 7

7

Reconnect the second 20-amp fused jumper between the battery positive voltage circuit of the cooling fan HIGH relay and the cooling fan motor supply voltage circuit of the cooling fan HIGH relay.

Does the right cooling fan operate in high speed?

Go to Step 10

Go to Step 8

8

  1. Install the cooling fan HIGH relay.
  2. Disconnect the right cooling fan electrical connector.
  3. Reconnect the second 20-amp fused jumper wire from the cooling fan motor supply voltage circuit of the right cooling fan electrical connector to the cooling fan motor ground circuit of the right cooling fan electrical connector.

Does the left cooling fan operate in high speed?

Go to Step 17

Go to Step 9

9

Reconnect 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 21

Go to Step 22

10

  1. Install the cooling fan HIGH relay.
  2. Disconnect the left cooling fan electrical connector.
  3. Reconnect the second 20-amp fused jumper wire from cooling fan motor supply voltage circuit of the left cooling fan electrical connector 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 18

Go to Step 11

11

Reconnect the second 20-amp fused jumper wire from battery positive voltage to the left cooling fan low reference circuit of the left cooling fan electrical connector.

Does the right cooling fan operate in high speed?

Go to Step 19

Go to Step 23

12

Does the right cooling fan operate in high speed?

Go to Step 13

Go to Step 16

13

  1. Disconnect the cooling fan HIGH relay.
  2. Connect a 20-amp fused jumper between the left cooling fan low reference circuit of the cooling fan HIGH relay and the ground circuit of the cooling fan HIGH relay.

Does the left cooling fan operate properly in high speed?

Go to Step 15

Go to Step 20

14

Inspect for poor connections at the cooling fan LOW 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 29

Go to Step 24

15

Inspect for poor connections at the cooling fan HIGH 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 29

Go to Step 25

16

Inspect for poor connections at the cooling fan S/P 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 29

Go to Step 26

17

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 29

Go to Step 27

18

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 29

Go to Step 28

19

Repair the left cooling fan motor supply voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 29

--

20

Repair the left cooling fan motor ground circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 29

--

21

Repair the right cooling fan motor ground circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 29

--

22

Repair the right cooling fan motor supply voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 29

--

23

Important: The S/P relay is located under the front bumper on the drivers side of the vehicle.

Repair the left cooling fan low reference circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 29

--

24

Replace the cooling fan LOW relay.

Did you complete the replacement?

Go to Step 29

--

25

Replace the cooling fan HIGH relay.

Did you complete the replacement?

Go to Step 29

--

26

Important: The S/P relay is located under the front bumper on the drivers side of the vehicle.

Replace the cooling fan S/P relay.

Did you complete the replacement?

Go to Step 29

--

27

Replace the right cooling fan. Refer to Engine Coolant Fan Motor Replacement .

Did you complete the replacement?

Go to Step 29

--

28

Replace the left cooling fan. Refer to Engine Coolant Fan Motor Replacement .

Did you complete the replacement?

Go to Step 29

--

29

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3