Circuit/System Description
The control module sends a pulse width modulation (PWM) signal of 0-12 volts via the cooling fan clutch control circuit to the cooling fan relay. The control module monitors the cooling fan clutch control circuit during vehicle operation. When the cooling fan is commanded ON by the control module, the control circuit is at a low voltage. When the cooling fan is commanded OFF, the control circuit is near battery voltage. The control module uses this PWM to control the position of the oil control valve located inside the cooling fan clutch. If, during operation, the control module detects an improper circuit condition on the cooling fan clutch control circuit, DTC P0480 will set.
The cooling fan relay sends a pulse width modulation (PWM) signal of 12-14 volts to the cooling fan clutch through the cooling fan clutch supply voltage circuit. The control module uses this PWM signal in order to control the speed of the cooling fan clutch. The signal controls the position of the oil control valve inside the cooling fan clutch. If the cooling fan RPM is different than the control module is expecting, DTC P0483 will set. The actual cooling fan RPM vs the desired cooling fan RPM is not always exactly the same. There can be up to an 800 RPM difference. If the control module detects that the cooling fan speed is over 6,800 RPM, DTC P0493 will set.
The cooling fan relay sends a pulse width modulation (PWM) signal, 12-14 volts, to the cooling fan by the cooling fan clutch supply voltage circuit. The control module uses the PWM signal, which controls the speed of the cooling fan clutch by controlling the position of the oil control valve inside the clutch. If the cooling fan clutch RPM is to high when the control module is commanding 0 percent, DTC P0495 will set.
The control module uses the cooling fan speed signal in order to determine the actual fan speed in relation to the desired fan speed. The control module uses the cooling fan speed signal in order to reduce the cooling fan noise and in order to maintain the powertrain cooling requirements. The control module supplies power and ground to the clutch hall effect sensor of the cooling fan clutch. The hall effect sensor returns a signal pulse through the speed signal circuit in response to the reluctor track, which is located inside the fan clutch. If, during operation, the control module detects a loss of the cooling fan speed signal, DTC P0526 will set.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
- 2: This step tests for the proper operation of the clutch hall effect sensor.
- 3: This step tests for the proper operation of the 5-volt reference circuit and of the low reference circuit of the cooling fan.
| 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 - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle | |
| 2 | Turn OFF the ignition. Disconnect the cooling fan clutch harness connector at the shroud. Connect a jumper wire between each of the following circuits: The 5-volt reference circuit The cooling fan speed signal circuit The low reference circuit Connect a DMM to the cooling fan speed signal circuit and ground. Turn ON the ignition, with the engine OFF. Manually rotate the cooling fan. Does the DMM voltage change? | 0-5 V | Go to Step 9 | Go to Step 3 |
| 3 | Disconnect the jumper wires. Measure the voltage between the 5-volt reference circuit and the low reference circuit of the cooling fan. Is the voltage measurement near than the specified value? | 5 V | Go to Step 4 | Go to Step 6 |
| 4 | Turn OFF the ignition. Probe the low reference circuit of the cooling fan clutch with a test lamp connected to battery positive voltage. Does the test lamp illuminate? | Go to Step 5 | Go to Step 8 | |
| 5 | Test the 5-volt reference circuit of the cooling fan clutch for a high resistance, or for an open. Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | Go to Step 14 | Go to Step 6 | |
| 6 | Test the cooling fan speed signal circuit of the cooling fan clutch for a short to ground, for a high resistance, or for an open. Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | Go to Step 14 | Go to Step 7 | |
| 7 | Test the cooling fan speed signal circuit of the cooling fan clutch for a short to voltage. Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | Go to Step 14 | Go to Step 10 | |
| 8 | Disconnect the powertrain control module (PCM). Test the low reference circuit of the cooling fan for a high resistance or for an open. Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | Go to Step 14 | Go to Step 11 | |
| 9 | Disconnect the jumper wires. Test the cooling fan speed signal circuit of the cooling fan clutch for an open. Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | Go to Step 14 | Go to Step 11 | |
| 10 | Inspect for a poor connection at the harness connector of the cooling fan clutch. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs . Did you find and correct the condition? | Go to Step 14 | Go to Step 12 | |
| 11 | Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs . Did you find and correct the condition? | Go to Step 14 | Go to Step 13 | |
| 12 | Replace the cooling fan clutch. Refer to Fan Clutch Replacement . Did you complete the replacement? | Go to Step 14 | ||
| 13 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 14 | ||
| 14 | Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running in the DTC. Does the DTC reset? | Go to Step 2 | System OK | |
DTC P1481
The numbers below refer to the step numbers on the diagnostic table.
- 2: The cooling fan noise should increase as the cooling fan clutch engages. It can take up to 2 minutes for full cooling fan clutch engagement. If cooling fan clutch is previously fully engaged, then there will not be a noticeable change in cooling fan noise. Compare noise to a known good vehicle. If fan noise is louder than the known good vehicle, answer Yes.
- 3: In the previous step the cooling fan clutch was fully engaged. This step tests to ensure that the cooling fan clutch will disengage. A noticeable noise difference should be heard between a fully engaged cooling fan clutch and a disengaged cooling fan clutch. The cooling fan clutch is completely disengaged when the excessive fan noise is not heard.
- 4: This step tests for the ability of the PCM to control cooling fan clutch speed. If answer to question is Yes, refer to all Diagnostic Aids.
- 5: This step verifies the ignition 1 voltage circuit of the cooling fan relay.
| 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 - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle | |
| 2 | With a scan tool, observe the Powertrain DTC list. Start the engine. Operate the vehicle within the Conditions for Running in the DTC. Does the scan tool indicate the DTC Failed this ignition cycle? | Go to Step 5 | Go to Step 3 | |
| 3 | IMPORTANT: DTC P1482, for 4.2L (LL8) will set when the cooling fan relay is disconnected. Turn OFF the ignition. Disconnect the coolant fan relay. Connect a 10-amp fused jumper wire between the cooling fan clutch supply voltage circuit of the cooling fan and the ignition 3 voltage circuit of the cooling fan relay. Start the engine. Raise engine speed to 2,000 RPM for 2 minutes. Does the cooling fan engage? | Go to Step 4 | Go to Step 5 | |
| 4 | IMPORTANT: Continuously excessive fan noise is due to the powertrain control module (PCM) commanding the cooling fan to 100 percent engaged or a mechanical failure. If the fan noise decreases during this step, then this DTC is due to an electrical malfunction. Replacing the cooling fan will not correct the condition. Turn OFF the ignition. Remove the 10-amp fused jumper wire. Install the cooling fan relay. Disconnect the cooling fan clutch connector. Start the engine. Raise engine speed to 2,000 RPM for 2 minutes. Does the cooling fan clutch disengage? | Go to Step 6 | Go to Step 16 | |
| 5 | Turn OFF the ignition. Disconnect the cooling fan relay. Turn ON the ignition, with the engine OFF. Probe the ignition 1 voltage circuit of the cooling fan relay with a test lamp connected a good ground. Does the test lamp illuminate? | Go to Step 6 | Go to Step 10 | |
| 6 | Test the cooling fan clutch control circuit of the cooling fan relay for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 18 | Go to Step 7 | |
| 7 | Test the cooling fan clutch control circuit of the cooling fan relay for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 18 | Go to Step 8 | |
| 8 | Connect a test lamp to the cooling fan clutch control circuit of the cooling fan relay and battery voltage. Start the engine. Command the fan control to 0 percent. Does the test lamp flash dim? | Go to Step 13 | Go to Step 9 | |
| 9 | Command the fan control to 100 percent. Does the test lamp flash bright? | Go to Step 12 | Go to Step 13 | |
| 10 | Inspect the Eng Fan fuse. Is the fuse open? | Go to Step 11 | Go to Step 14 | |
| 11 | Test the cooling fan clutch control circuit of the cooling fan relay for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 18 | Go to Step 14 | |
| 12 | Inspect for poor connections at the cooling fan relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 18 | Go to Step 15 | |
| 13 | Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 18 | Go to Step 17 | |
| 14 | Repair the ignition 1 voltage circuit of the cooling fan relay. Refer to Wiring Repairs . Did you complete the repair? | Go to Step 18 | ||
| 15 | Replace the cooling fan relay. Did you complete the replacement? | Go to Step 18 | ||
| 16 | Replace the cooling fan clutch. Refer to Fan Clutch Replacement . Did you complete the replacement? | Go to Step 18 | ||
| 17 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 18 | ||
| 18 | Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text. Does the DTC reset? | Go to Step 2 | System OK | |
| IMPORTANT |
|---|
| DTC P1482, for 4.2L (LL8) will set when the cooling fan relay is disconnected. |
| IMPORTANT |
|---|
| Continuously excessive fan noise is due to the powertrain control module (PCM) commanding the cooling fan to 100 percent engaged or a mechanical failure. If the fan noise decreases during this step, then this DTC is due to an electrical malfunction. Replacing the cooling fan will not correct the condition. |
DTC P1482
The numbers below refer to the step numbers on the diagnostic table.
- 2: This step ensures that the DTC has failed this ignition cycle. If the scan tool displays Passed, the answer is No.
- 3: The cooling fan noise should increase as the cooling fan clutch engages. It can take up to 2 minutes for full cooling fan clutch engagement. If cooling fan clutch is previously fully engaged, then there will not be a noticeable change in cooling fan noise. Compare noise to a known good vehicle. If fan noise is louder than the known good vehicle, answer Yes.
- 4: In the previous step the cooling fan clutch was fully engaged. This step tests to ensure that the cooling fan clutch will disengage. A noticeable noise difference should be heard between a fully engaged cooling fan clutch and a disengaged cooling fan clutch. The cooling fan clutch is completely disengaged when the excessive fan noise is not heard.
- 5: This step inspects for a mechanical condition which causes the DTC to set.
- 6: This step tests for voltage on the cooling fan clutch supply voltage circuit of the cooling fan clutch. The cooling fan clutch connector is a seal connector. You must use jumper wires for testing or damage to wiring or connector could happen.
- 7: This step tests the cooling fan relay for a PWM signal on the cooling fan clutch supply voltage circuit of the cooling fan clutch.
| 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 - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle | |
| 2 | With a scan tool, observe the Powertrain DTC list. Start the engine. Operate the vehicle within the Conditions for Running in the DTC. Does the scan tool indicate the DTC Failed this ignition cycle? | Go to Step 5 | Go to Step 3 | |
| 3 | IMPORTANT: DTC P1482, for 4.2L (LL8) will set when the cooling fan relay is disconnected. Turn OFF the ignition. Disconnect the coolant fan relay. Connect a 10-amp fused jumper wire between the cooling fan clutch supply voltage circuit of the cooling fan and the ignition 3 voltage circuit of the cooling fan relay. Start the engine. Raise engine speed to 2,000 RPM for 2 minutes. Does the cooling fan engage? | Go to Step 4 | Go to Step 5 | |
| 4 | IMPORTANT: Continuously excessive fan noise is due to the powertrain control module (PCM) commanding the cooling fan to 100 percent engaged or a mechanical failure. If the fan noise decreases during this step, then this DTC is due to an electrical malfunction. Replacing the cooling fan clutch will not correct the condition. Turn OFF the ignition. Remove the 10-amp fused jumper wire. Install cooling fan relay. Disconnect the cooling fan clutch connector. Start the engine. Raise engine speed to 2,000 RPM for 2 minutes. Does the cooling fan clutch disengage? | Go to Step 5 | Go to Step 17 | |
| 5 | Turn OFF the ignition. Inspect the cooling fan and the drive belt for the following conditions: A cracked drive belt A loose or a worn drive belt A misrouted drive belt Oil leaks at the cooling fan clutch A free-spinning cooling fan A seized cooling fan clutch A broken cooling fan If the above conditions exist, refer to one of the following procedures: Cooling Fan and Shroud Replacement Drive Belt Falls Off and Excessive Wear Diagnosis Drive Belt Tensioner Diagnosis Did you find and correct the condition? | Go to Step 19 | Go to Step 6 | |
| 6 | Disconnect the cooling fan clutch connector at the fan shroud. Connect a jumper wire between each of the cooling fan clutch circuits. Connect a DMM between the clutch supply voltage circuit of the cooling fan clutch and ground. Start the engine. Command the fan control to 0 percent. Does the voltage measure greater than the specified value? | 0.16 V | Go to Step 9 | Go to Step 7 |
| 7 | Command the fan control to 100 percent. Does the voltage fluctuate? | Go to Step 10 | Go to Step 8 | |
| 8 | Turn OFF the ignition. Disconnect the cooling fan relay. Turn ON the ignition, with the engine OFF. Probe the ignition 1 voltage circuit of the cooling fan relay with a test lamp connected to a good ground. Does the test lamp illuminate? | Go to Step 11 | Go to Step 16 | |
| 9 | Disconnect the cooling fan relay. Does the voltage measure greater than the specified value? | 0.16 V | Go to Step 13 | Go to Step 10 |
| 10 | Test the cooling fan clutch ground for an open. Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | Go to Step 19 | Go to Step 15 | |
| 11 | Test the ground circuit of the cooling fan relay for an open or a high resistance. Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | Go to Step 19 | Go to Step 12 | |
| 12 | Test the clutch supply voltage circuit of the cooling fan clutch for an open or a short to ground. Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | Go to Step 19 | Go to Step 14 | |
| 13 | Test the clutch supply voltage circuit of the cooling fan clutch for a short to voltage. Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | Go to Step 19 | ||
| 14 | Inspect for poor connections at the cooling fan relay. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs . Did you find and correct the condition? | Go to Step 19 | Go to Step 18 | |
| 15 | Inspect for poor connections at the harness connector of the cooling fan clutch. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs . Did you find and correct the condition? | Go to Step 19 | Go to Step 17 | |
| 16 | Repair the ignition 1 voltage circuit of the cooling fan relay. Refer to Wiring Repairs . Did you find and correct the condition? | Go to Step 19 | ||
| 17 | Replace the cooling fan clutch. Refer to Fan Clutch Replacement . Did you complete the replacement? | Go to Step 19 | ||
| 18 | Replace the cooling fan relay. Did you complete the replacement? | Go to Step 19 | ||
| 19 | IMPORTANT: Follow this procedure in order to clear DTC P1484 after making a repair. Use the Clear DTC Information function of the scan tool. Perform an ignition key cycle. Operate the vehicle within the Conditions for Running in the DTC. Does the DTC reset? | Go to Step 2 | System OK | |
| IMPORTANT |
|---|
| DTC P1482, for 4.2L (LL8) will set when the cooling fan relay is disconnected. |
| IMPORTANT |
|---|
| Continuously excessive fan noise is due to the powertrain control module (PCM) commanding the cooling fan to 100 percent engaged or a mechanical failure. If the fan noise decreases during this step, then this DTC is due to an electrical malfunction. Replacing the cooling fan clutch will not correct the condition. |
| IMPORTANT |
|---|
| Follow this procedure in order to clear DTC P1484 after making a repair. |
DTC P1484
| IMPORTANT | Review the system operation in order to familiarize yourself with the system functions. Refer to Cooling System Description and Operation . |
The optional coolant heater operates using 110 volt AC external power and is designed to warm the coolant in the engine block area for improved starting in very cold weather. There is an internal thermal switch in the power cord that prevents operation above -18°C (0°F). The coolant heater helps reduce fuel consumption when a cold engine is warming up. The unit is equipped with a detachable AC power cord. A weather shield on the cord is provided to protect the plug when not in use.
The numbers below refer to the step numbers on the diagnostic table.
- 2: There should be no binding or increased resistance as the cooling fan clutch is rotated.
- 4: The cooling fan noise should increase as the cooling fan clutch engages. It can take up to 2 minutes for full cooling fan clutch engagement. If cooling fan clutch is previously fully engaged, then there will not be a noticeable change in cooling fan noise. Compare noise to a known good vehicle. If fan noise is louder than the known good vehicle, then answer Yes.
- 5: In the previous step the cooling fan clutch was fully engaged. This step tests to ensure that the cooling fan clutch will disengage. A noticeable noise difference should be heard between a fully engaged cooling fan clutch and a disengaged cooling fan. The cooling fan clutch is completely disengaged when the excessive fan noise is not heard.
- 7: This step clears DTCs that were set during previous steps. Test driving the vehicle will attempt to set DTCs not previous found in the Engine Cooling Diagnostic Check. If no DTC is set, the condition is a normal operation of the cooling fan.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Engine Cooling Schematics Connector End View Reference: Cooling System Connector End Views DEFINITION: The cooling fan clutch has excessive fan noise. | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle |
| 2 | Rotate the cooling fan 3 complete revolutions? Is the resistance of the cooling fan clutch even throughout each rotation? | Go to Step 4 | Go to Step 3 |
| 3 | Inspect the cooling fan clutch for proper installation. Refer to Fan Clutch Replacement . Did you find and correct the condition? | Go to Step 13 | Go to Step 11 |
| 4 | IMPORTANT: DTC P1482 for 4.2L (LL8) and P0480 for 5.3L (LM4) will set when the cooling fan relay is disconnected. Turn OFF the ignition. Disconnect the coolant fan relay. Connect a 10-amp fused jumper wire between the cooling fan clutch supply voltage circuit of the cooling fan and the ignition 3 voltage circuit of the cooling fan relay. Start the engine. Raise engine speed to 2,000 RPM for 2 minutes. Does the cooling fan clutch engage? | Go to Step 5 | Go to Step 8 |
| 5 | IMPORTANT: Continuous excessive fan noise is due to a mechanical failure. If the fan noise decreases during this step, then there is an electrical malfunction. Replacing the cooling fan clutch will not correct the condition. Turn OFF the ignition. Remove the 10-amp fused jumper wire. Install the cooling fan relay. Disconnect the cooling fan clutch connector. Start the engine. Raise the engine speed to 2,000 RPM for 2 minutes. Does the cooling fan disengage? | System OK | Go to Step 6 |
| 6 | Turn OFF the ignition. If the A/C system was operating, then wait for approximately 2 minutes. Install J 43600 ACR 2000 Air Conditioning Service Center. Turn ON the ignition, with the engine OFF. With a scan tool, observe the A/C High Side Pressure Sensor parameter. Compare the A/C high side pressure on the scan tool to the high side pressure on J 43600 . Are the high side pressure values within 138 kPa (20 psi) of each other? | Go to Step 7 | Go to Step 9 |
| 7 | Turn OFF the ignition. Connect the cooling fan clutch connector. Turn ON the ignition, with the engine OFF. With a scan tool, clear all DTCs. Start the engine. Test drive the vehicle. With a scan tool, observe the DTC list. Does the scan tool display any cooling system DTCs? | Go to Diagnostic Trouble Code (DTC) List - Vehicle | System OK |
| 8 | Inspect for poor connections at the harness connector of the cooling fan clutch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 13 | Go to Step 11 |
| 9 | Inspect for poor connections at the harness connector of the A/C high side pressure sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 12 | Go to Step 10 |
| 10 | Replace the A/C refrigerant pressure sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement . Did you complete the replacement? | Go to Step 13 | |
| 11 | Replace the cooling fan clutch. Refer to Fan Clutch Replacement . Did you complete the replacement? | Go to Step 13 | |
| 12 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 8 |
| 13 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3 |
| IMPORTANT |
|---|
| DTC P1482 for 4.2L (LL8) and P0480 for 5.3L (LM4) will set when the cooling fan relay is disconnected. |
| IMPORTANT |
|---|
| Continuous excessive fan noise is due to a mechanical failure. If the fan noise decreases during this step, then there is an electrical malfunction. Replacing the cooling fan clutch will not correct the condition. |
Excessive Fan Noise