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: The engine cooling fan motor is 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

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the low speed fan relay ON and OFF.

Does the cooling fan turn ON and OFF with each command?

Go to Step 3

Go to Step 4

3

With a scan tool, command the high speed fan relay ON and OFF.

Does the cooling fan turn ON and OFF with each command?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 7

4

  1. Disconnect the cooling fan 1 relay.
  2. Turn ON the ignition, with the engine OFF.
  3. Probe the battery positive voltage circuit of the cooling fan 1 relay with a test lamp connected to a good ground.

Does the test lamp illuminate?

Go to Step 5

Go to Step 11

5

  1. Connect the cooling fan 1 relay.
  2. Disconnect the cooling fan.
  3. Probe the low speed cooling fan supply voltage circuit with a test lamp connected to a good ground.
  4. With a scan tool, command the low speed fan relay ON and OFF.

Does the test lamp turn ON and OFF with each command?

Go to Step 6

Go to Step 9

6

Probe the ground circuit of the cooling fan with a test lamp connected to battery positive voltage.

Does the test lamp illuminate?

Go to Step 13

Go to Step 12

7

  1. Disconnect the cooling fan 2 relay.
  2. Turn ON the ignition, with the engine OFF.
  3. Probe the battery positive voltage circuit of the cooling fan 2 relay with a test lamp connected to a good ground.

Does the test lamp illuminate?

Go to Step 8

Go to Step 11

8

  1. Connect the cooling fan 2 relay.
  2. Disconnect the cooling fan.
  3. Probe the high speed cooling fan supply voltage circuit with a test lamp connected to a good ground.
  4. With a scan tool, command the high speed fan relay ON and OFF.

Does the test lamp turn ON and OFF with each command?

Go to Step 13

Go to Step 10

9

Test the low speed cooling fan supply voltage circuit for a high resistance and an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 15

10

Test the high speed cooling fan supply voltage circuit for a high resistance and an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 16

11

Repair the battery positive voltage circuit of the cooling fans. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 21

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12

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

Did you complete the repair?

Go to Step 21

--

13

Inspect for poor connections at the harness connector of the cooling fan. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 17

14

Inspect for poor connections at the harness connector of the powertrain control module (PCM). 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 21

Go to Step 18

15

Inspect for poor connections at the harness connector of the cool 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 21

Go to Step 19

16

Inspect for poor connections at the harness connector of the cool 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 21

Go to Step 20

17

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

Did you complete the replacement?

Go to Step 21

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18

Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Go to Step 21

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19

Replace the cool fan 1 relay. Refer to Cooling Fan Relay Replacement .

Did you complete the replacement?

Go to Step 21

--

20

Replace the cool fan 2 relay. Refer to Cooling Fan Relay Replacement .

Did you complete the replacement?

Go to Step 21

--

21

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3