Checking The Cooling Fan Operation
CHECKING THE COOLING FAN OPERATION
Low Speed Operation
Hi Speed 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 fans operate in series, splitting the 12 Volt source between the two cooling fan motors. During high speed mode, the cooling fan motors operate in parallel to one another, with each cooling fan motor receiving a separate 12 Volt source.
During low speed mode: The TIPM 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 Motor 1. Current flows through the motor 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 2. The (Z901) Ground circuit provides the ground path for the Cooling Fan series circuit.
During High speed mode: The TIPM 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 (Z901) 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 to Cooling Fan Motor 1. The (N210) Cooling Fan Lo-Hi Control circuit connects to the (Z901) Ground circuit through the Lo-Hi Fan Relay to provide the ground path for Cooling Fan Motor 1.
1.
NOTE: Diagnose and repair any Cooling Fan Relay control circuit DTCs before proceeding with this test.
COOLING FAN OPERATION (LOW SPEED)
1. With a scan tool, actuate the cooling fans in low speed operation.
NOTE: During low speed actuation the Cooling Fan Motors are barely audible.
Are the Cooling Fan Motors operating?
Yes
- Go To 2
No
- Go To 3
2. COOLING FAN OPERATION (HIGH SPEED)
1. With a scan tool, actuate the cooling fans in high speed operation.
NOTE: During high speed actuation the Cooling Fan Motors are easily audible.
Are both Cooling Fan Motors operating?
Yes
- The Cooling Fan Motors are operating properly.
No, Cooling Fan Motor 1 is inoperative
- Go To 8
No, Cooling Fan Motor 2 is inoperative
- Go To 11
3. CHECK THE (A16) COOLING FAN 12 VOLT SUPPLY CIRCUIT
1. Turn the ignition on.
2. Remove the Hi-Med. Fan Relay.
3. Using a 12-Volt test light connected to ground, probe the (A16) Cooling Fan 12 Volt Supply circuit at the Relay 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
- Go To 4
No
- Repair the (A16) Cooling Fan 12 Volt Supply circuit for an open.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.
4. CHECK THE (N23) COOLING FAN MOTOR 1 OUTPUT VOLTAGE
1. Disconnect the Cooling Fan Motor 1 harness connector.
2. Using a Voltmeter connected to ground, probe the (N23) Cooling Fan Motor 1 Output circuit at the Cooling Fan Motor 1 harness connector.
NOTE: The voltage reading should be approximately Battery voltage.
Is the voltage reading equal to Battery voltage?
Yes
- Go To 5
No
- Repair the (N23) Cooling Fan Motor 1 Output circuit for an open or high resistance.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.
5. CHECK THE COOLING FAN MOTOR 2 OUTPUT VOLTAGE
1. Reconnect the Cooling Fan Motor 1 harness connector.
2. Disconnect the Cooling Fan Motor 2 harness connector.
NOTE: Cooling Fan Motor 1 must be connected before checking for voltage at the (N24) circuit.
3. Measure the voltage of the (N24) Cooling Fan Motor 2 Output circuit at the Cooling Fan Motor 2 harness connector.
NOTE: The voltage reading should be approximately Battery voltage.
Is the voltage reading equal to Battery voltage?
Yes
- Go To 6
No
- Go To 7
6. CHECK THE (Z901) GROUND CIRCUIT
1. Using a 12-Volt test light connected to 12 Volts, probe the (Z901) Ground circuit at the Cooling Fan Motor 2 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 Motor 2.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.
No
- Repair the (Z901) Ground circuit for an open.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.
7. CHECK THE COOLING FAN MOTOR 2 SUPPLY
1. Turn the ignition off.
2. Disconnect the Cooling Fan Motor 1 harness connector.
3. Measure the resistance from the (N210) Cooling Fan Lo-Hi Control circuit at the Cooling Fan Motor 1 harness connector and the (N24) Cooling Fan Motor 2 Output circuit at the Cooling Fan Motor 2 harness connector.
Is the resistance below 5.0 Ohms?
Yes
- Replace the Cooling Fan Motor 1.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.
No
- Repair the open or high resistance in the circuit or circuits. Try switching the Hi-Lo Fan Relay with a known good relay and rechecking the circuit before checking the (N210) and (N24) circuits for an open.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.
8. CHECK THE (A16) COOLING FAN 12 VOLT SUPPLY CIRCUIT
1. Turn the ignition on.
2. Remove the Hi-Med. Fan Relay.
3. Using a 12-Volt test light connected to ground, probe the (A16) Cooling Fan 12 Volt Supply circuit at the Relay 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
- Go To 9
No
- Repair the (A16) Cooling Fan 12 Volt Supply circuit for an open.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.
9. CHECK THE (N23) COOLING FAN MOTOR 1 OUTPUT VOLTAGE
1. Connect a jumper between the (A16) Cooling Fan 12 Volt Supply circuit and the (N23) Cooling Fan Motor 1 Output circuit at the Hi-Med. Fan Relay.
2. Disconnect the Cooling Fan Motor 1 harness connector.
3. Using a Voltmeter connected to ground, probe the (N23) Cooling Fan Motor 1 Output circuit at the Cooling Fan Motor 1 harness connector.
NOTE: The voltage reading should be approximately Battery voltage.
Is the voltage reading equal to Battery voltage?
Yes
- Go To 10
No
- Repair the (N23) Cooling Fan Motor 1 Output circuit for an open or high resistance.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.
10. CHECK THE GROUND CIRCUIT
1. With a scan tool, actuate the cooling fans in high speed operation.
2. Using a 12-Volt test light connected to 12 Volts, probe the (N210) Cooling Fan Lo-Hi Control circuit at the Cooling Fan Motor 1 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 Motor 1.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.
No
- Repair the open or high resistance in the circuit or circuits. Try switching the Hi-Lo Fan Relay with a known good relay and rechecking the circuit before checking the (N210) and (Z901) circuits for an open.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.
11. CHECK THE (A16) COOLING FAN 12 VOLT SUPPLY CIRCUIT
1. Turn the ignition on.
2. Remove the Series-Parallel Fan Relay.
3. Using a 12-Volt test light connected to ground, probe the (A16) Cooling Fan 12 Volt Supply circuit at the Relay 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
- Go To 12
No
- Repair the (A16) Cooling Fan 12 Volt Supply circuit for an open.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.
12. CHECK THE (N24) COOLING FAN MOTOR 2 OUTPUT VOLTAGE
1. Connect a jumper between the (A16) Cooling Fan 12 Volt Supply circuit and the (N24) Cooling Fan Motor 2 Output circuit at the Series-Parallel Fan Relay.
2. Disconnect the Cooling Fan Motor 2 harness connector.
3. Using a Voltmeter connected to ground, probe the (N24) Cooling Fan Motor 2 Output circuit at the Cooling Fan Motor 2 harness connector.
NOTE: The voltage reading should be approximately Battery voltage.
Is the voltage reading equal to Battery voltage?
Yes
- Go To 13
No
- Repair the (N24) Cooling Fan Motor 2 Output circuit for an open or high resistance.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.
13. CHECK THE (Z901) GROUND CIRCUIT
1. Using a 12-Volt test light connected to 12 Volts, probe the (Z901) Ground circuit at the Cooling Fan Motor 2 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 Motor 2.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.
No
- Repair the (Z901) Ground circuit for an open or high resistance.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.