GM Service Manual Online
For 1990-2009 cars only

Cooling Fan Inoperative 3.4L LA1

Step

Action

Yes

No

Schematic Reference: Engine Cooling Schematics

Connector End View Reference: Cooling System Connector End Views

DEFINITION: One or both engine cooling fan motors do not operate properly in high or low speed.

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  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 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 13

4

Test the fused battery positive voltage circuit of the cooling fan 1 relay for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 30

Go to Step 5

5

Test the cooling fan motor supply voltage circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 30

Go to Step 6

6

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

Do both cooling fans operate in low speed?

Go to Step 15

Go to Step 7

7

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

Do both cooling fans operate in low speed?

Go to Step 16

Go to Step 8

8

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

Does the right cooling fan operate in high speed?

Go to Step 11

Go to Step 9

9

  1. Install the cooling fan mode relay.
  2. Disconnect the right cooling fan electrical connector.
  3. Connect 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 18

Go to Step 10

10

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 22

Go to Step 23

11

  1. Install the cooling fan mode relay.
  2. Disconnect the left cooling fan electrical connector.
  3. Connect the second 20-amp fused jumper wire from the 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 19

Go to Step 12

12

Connect 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 20

Go to Step 24

13

Is the right cooling fan operating properly in high speed?

Go to Step 14

Go to Step 17

14

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

Does the left cooling fan operate properly in high speed?

Go to Step 16

Go to Step 21

15

Inspect for poor connections at the cooling 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 30

Go to Step 25

16

Inspect for poor connections at the cooling fan mode 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 30

Go to Step 26

17

Inspect for poor connections at the cooling 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 30

Go to Step 27

18

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 30

Go to Step 28

19

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 30

Go to Step 29

20

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

Did you complete the repair?

Go to Step 30

--

21

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

Did you complete the repair?

Go to Step 30

--

22

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

Did you complete the repair?

Go to Step 30

--

23

Important: Do NOT remove the 20-amp fused jumper wire connected during this step. Use a second 20-amp fused jumper while performing the following steps.

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

Did you complete the repair?

Go to Step 30

--

24

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

Did you complete the repair?

Go to Step 30

--

25

Replace the cooling fan 1 relay.

Did you complete the repair?

Go to Step 30

--

26

Replace the cooling fan mode relay.

Did you complete the repair?

Go to Step 30

--

27

Replace the cooling fan 2 relay.

Did you complete the repair?

Go to Step 30

--

28

Replace the right cooling fan. Refer to Engine Cooling Fan Replacement .

Did you complete the repair?

Go to Step 30

--

29

Replace the left cooling fan. Refer to Engine Cooling Fan Replacement .

Did you complete the repair?

Go to Step 30

--

30

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3