The Cooling Fan Relay 1 or ELEC FAN LOW relay, and Cooling Fan Relay 2 and 3 or ELEC FAN HIGH relay and the ELEC FAN CONT relay are controlled by the engine control module (ECM). The ELEC FAN HIGH relay and the ELEC FAN CONT relay share one control circuit. Battery positive voltage is supplied to the relay coil. The ECM monitors the voltage level on the control circuit of the relay. When the relay is off, voltage level should be near battery voltage on the control circuit of the relay. When the relay is commanded on, voltage level will be low on the control circuit of the relay. The ECM will provide ground on the control circuit of the relay using a low side driver. If the ECM detects a improper voltage level on the control circuit of the relay, a DTC will set.
This diagnostic procedure supports the following DTCs:
• | DTC P0480 Cooling Fan Relay 1 Control Circuit |
• | DTC P0481 Cooling Fan Relay 2 and 3 Control Circuit |
• | The ignition is ON or the engine is operating. |
• | The ignition 1voltage is more than 10 volts. |
• | DTCs P0480 and P0481 run continuously once the above conditions are met. |
The ECM detects one of the following conditions on the control circuit of one of the relays for 25 seconds:
• | An open |
• | A short to ground |
• | A short to voltage |
• | The control module stores the DTC information into memory when the diagnostic runs and fails. |
• | The malfunction indicator lamp (MIL) will not illuminate. |
• | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records. |
• | The driver information center, if equipped, may display a message. |
• | A current DTC Last Test Failed clears when the diagnostic runs and passes. |
• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. |
• | Clear the DTC with a scan tool. |
• | For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
• | The following tables illustrate the ELEC FAN LOW relay, ELEC FAN HIGH relay and the ELEC FAN CONT relay terminal locations in the underhood fuse block: |
ELEC FAN LOW Relay Terminal Identification | |
---|---|
B+ - Switch | Control |
B+ - Coil | Auxiliary Cooling Fan Supply Voltage |
Front of Vehicle |
ELEC FAN HIGH Relay Terminal Identification | |
---|---|
B+ - Switch | Control |
B+ - Coil | Main Cooling Fan Supply Voltage |
Front of Vehicle |
ELEC FAN CONT Relay Terminal Identification | |
---|---|
Ground | Control |
Main Cooling Fan Supply Voltage | -- |
B+ - Coil | Voltage from Auxiliary Cooling Fan |
Front of Vehicle |
The numbers below refer to the step numbers on the diagnostic table.
A test lamp that remains illuminated indicates a short to ground on the control circuit. A test lamp that does not illuminate indicates an open or short to voltage on the control circuit.
This step tests the control circuit for high resistance.
Step | Action | Values | Yes | No | ||||||
---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Cooling Schematics Connector End View Reference: Cooling System Connector End Views | ||||||||||
1 | Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | |||||||
2 |
Does the ELEC FAN LOW relay turn ON and OFF with each command? | -- | Go to Step 3 | Go to Step 4 | ||||||
3 | With a scan tool, command the Fans High Speed ON and OFF. Do the ELEC FAN HIGH and ELEC FAN CONT relays turn ON and OFF with each command? | -- | Go to Diagnostic Aids | Go to Step 4 | ||||||
4 |
Does the test lamp illuminate? | -- | Go to Step 5 | Go to Step 13 | ||||||
5 |
Does the test lamp turn ON and OFF? | -- | Go to Step 7 | Go to Step 6 | ||||||
Does the test lamp remain illuminated? | -- | Go to Step 9 | Go to Step 10 | |||||||
7 |
Is the resistance less than the specified value? | 3 ohms | Go to Step 8 | Go to Step 13 | ||||||
Important: Use the J 35616-200 Test Lamp Kit for this test. If the J 35616-200 is not available, use a test lamp that measures between 25-30 ohms. Is the voltage less than the specified value? | 2.5 V | Go to Step 11 | Go to Step 10 | |||||||
9 | Test the control circuit of the affected relay 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 16 | Go to Step 12 | ||||||
10 | Test the control circuit of the affected relay for one of the following conditions:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 12 | ||||||
11 | Test for shorted terminals and poor connections at the affected relay. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 14 | ||||||
12 | Test for shorted terminals and poor connections at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 15 | ||||||
13 | Repair an open or high resistance in the battery positive voltage circuit of the affected relay coil. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 16 | -- | ||||||
14 | Replace the affected relay. Refer to Relay Replacement in Wiring Systems. Did you complete the replacement? | -- | Go to Step 16 | -- | ||||||
15 | Replace the ECM. Refer to Engine Control Module Replacement in Engine Controls - 2.5L. Did you complete the replacement? | -- | Go to Step 16 | -- | ||||||
16 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 17 | ||||||
17 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List in Engine Controls - 2.5L | System OK |