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Checking The Cooling Fan Operation





CHECKING THE COOLING FAN OPERATION





For a complete wiring diagram, refer to the Wiring Information.

Cooling Fan Modes of Operation

The two speed cooling fan system uses three relays to control the cooling fan operation. These are the Series-Parallel Fan Relay, Lo-Hi Fan Relay and Hi-Med. Fan Relay. During low speed mode, the cooling fan and cooling fan resistor operate in series, splitting the 12 Volt source between the the resistor and the cooling fan motor. During high speed mode, the cooling fan motor and resistor operate in parallel to one another, with each receiving a separate 12 Volt source.

During low speed mode: The PCM grounds the (N201) Fan Relay Control circuit, closing the relay to connect the (A16) Cooling Fan 12 Volt Supply circuit to the (N23) Cooling Fan Motor 1 Output circuit. The (N23) Cooling Fan Motor 1 Output circuit supplies 12 Volts DC to cooling fan resistor. Current flows through the resistor to the (N210) Cooling Fan Lo-Hi Control circuit. The current passes through the Lo-Hi Fan Relay to the (N24) Cooling Fan Motor 2 Output circuit and on to Cooling Fan Motor. The (Z903) Ground circuit provides the ground path for the Cooling Fan series circuit.

During High speed mode: The PCM grounds the (N201) Fan Relay Control circuit and the (N112) Fan Relay Control circuit, closing all three Cooling Fan Relays. The (A16) Cooling Fan 12 Volt Supply circuit connects to the (N24) Cooling Fan Motor 2 Output circuit through the Series-Parallel Fan Relay and provides 12 Volts to Cooling Fan Motor 2. The (Z903) Ground circuit provides the ground for Cooling Fan Motor 2. The (A16) Cooling Fan 12 Volt Supply circuit connects to the (N23) Cooling Fan Motor 1 Output circuit through the Hi-Med. Fan Relay and provides 12 Volts through the cooling fan resistor. The (N210) Cooling Fan Lo-Hi Control circuit connects to the (Z903) Ground circuit through the Lo-Hi Fan Relay to provide the ground path for the cooling fan resistor.

1. RADIATOR FAN OPERATION

NOTE: Diagnose and repair any Cooling Fan Relay control circuit DTCs before proceeding with this test.

1. Turn the ignition on, engine not running.
2. Using a scan tool, actuate the low speed fan.
3. Using a scan tool, actuate the high speed fan.

NOTE: During high speed actuation the Cooling Fan Motor is easily audible.

Does the fan operate in both speeds?

Yes

- The cooling fan is operating normal at this time.
- Perform the INTERMITTENT CONDITION test procedure. Intermittent Condition Test

No, the cooling fan does not operate for either speed

- Go To 2

No, only the low speed is operating

- Go To 8

No, only the high speed is operating

- Go To 10

2. RADIATOR FAN BATTERY SUPPLY CIRCUIT
1. Stop the actuation.
2. Remove the Radiator Fan Series/Parallel Relay from the PDC.
3. Using a 12-Volt test light connected to ground, probe the Battery Feed circuit at the relay connector (terminal 30).

Is the test light illuminated and bright?

Yes

- Go To 3

No

- Inspect the 50 amp Radiator Fan fuse. If the fuse is ok, replace the Powertrain Distribution Center (PDC).
- If the fuse is open, Go To 5
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

3. EXCESSIVE RESISTANCE IN THE (N210) CIRCUIT
1. Turn the ignition off.
2. Measure the resistance of the (N210) circuit from the Cooling Fan Module harness connector to the Radiator Fan Series/Parallel Relay connector (terminal 87).

Is the resistance below 5.0 Ohms?

Yes

- Go To 4

No

- Repair the (N210) circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

4. CHECK THE (Z903) GROUND CIRCUIT




1. Using a 12-Volt test light connected to 12 Volts, probe the (Z903) Ground circuit at the Cooling Fan Module harness connector.

NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.

Is the test light illuminated and bright?

Yes

- Replace the Cooling Fan Module.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Repair the (Z903) Ground circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

5. (N210) CIRCUIT SHORTED TO GROUND




1. Turn the ignition off.
2. Disconnect the Cooling Fan Module harness connector.
3. Measure the resistance between ground and the (N210) circuit at the Cooling Fan Module harness connector.

Is the resistance below 10k Ohms?

Yes

- Repair the short to ground in the (N210) circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 6

6. (N24) CIRCUIT SHORTED TO GROUND




1. Remove the Radiator Fan Medium/High Relay and the Radiator Fan Low/High Relay from the PDC.
2. Measure the resistance between ground and the (N24) circuit at the Cooling Fan Module harness connector.

Is the resistance below 10k Ohms?

Yes

- Repair the short to ground in the (N24) circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 7

7. (N23) CIRCUIT SHORTED TO GROUND




1. Measure the resistance between ground and the (N23) circuit at the Cooling Fan Module harness connector.

Is the resistance below 10k Ohms?

Yes

- Repair the (N23) circuit for an open or short to ground.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace the Cooling Fan Module.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

8. RADIATOR FAN BATTERY SUPPLY CIRCUIT
1. Stop the actuation.
2. Remove the Radiator Fan Series/Parallel Relay from the PDC.
3. Using a 12-Volt test light connect to ground, probe the Battery Feed circuit at the relay connector (terminal 30).

Is the test light illuminated and bright?

Yes

- Go To 9

No

- Replace the Powertrain Distribution Center (PDC).
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

9. CHECK RADIATOR FAN SERIES/PARALLEL RELAY
1. Connect a jumper across terminal 30 and terminal 87 at the Radiator Fan Series/Parallel Relay connector in the PDC.

Does the Cooling Fan operate with the jumper in place?

Yes

- Replace the Radiator Fan Series/Parallel Relay.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace the Powertrain Distribution Center (PDC).
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

10. RADIATOR FAN BATTERY SUPPLY CIRCUIT
1. Stop the actuation.
2. Remove the Radiator Fan Medium/High Relay from the PDC.
3. Using a 12-Volt test light connect to ground, probe the Battery Feed circuit at the relay connector (terminal 30).

Is the test light illuminated and bright?

Yes

- Go To 11

No

- Replace the Powertrain Distribution Center (PDC).
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

11. EXCESSIVE RESISTANCE IN THE (N24) CIRCUIT
1. Turn the ignition off.
2. Disconnect the Cooling Fan Module harness connector.
3. Measure the resistance of the (N24) circuit between the Cooling Fan Module harness connector and terminal 87 of the Radiator Fan Medium/High Relay connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 12

No

- Repair the (N24) circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

12. EXCESSIVE RESISTANCE IN THE (N23) CIRCUIT
1. Remove the Radiator Fan Low/High Relay in the PDC.
2. Measure the resistance of the (N23) circuit between the Cooling Fan Module harness connector and terminal 30 of the Radiator Fan Low/High Relay connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 13

No

- Repair the (N23) circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

13. EXCESSIVE RESISTANCE IN THE (N210) RAD FAN RELAY OUTPUT CIRCUIT
1. Measure the resistance of the (N210) circuit between the Cooling Fan Module harness connector and terminal 87A of the Radiator Fan Low/High Relay connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 14

No

- Repair the (N210) circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

14. CHECK THE (Z903) GROUND CIRCUIT




1. Using a 12-Volt test light connected to 12 Volts, probe the (Z903) Ground circuit at the Cooling Fan Module harness connector.

NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.

Is the test light illuminated and bright?

Yes

- Replace the Cooling Fan Module.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Repair the (Z903) Ground circuit for an open.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

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