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P0481




DTC P0480 or P0481 (LUW)

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructionsprovides an overview of each diagnostic category.

DTC Descriptor
DTC P0480
- Cooling Fan Relay 1 Control Circuit

DTC P0481
- Cooling Fan Relay 2 Control Circuit

Diagnostic Fault Information














Circuit/System Description

The engine control module (ECM) commands the fan ON in either high speed, medium speed, or low speed, depending on cooling requirements. In low speed, the fan is turned ON at a reduced speed. In medium speed, the fan is turned ON at a higher reduced speed. In high speed, the fan is turned ON at full speed.

In low speed operation, the ECM provides ground from ECM terminal 44 X1 to the cooling fan relay. The cooling fan relay activates and provides ground to the coils of the cooling fan low speed relay and the cooling fan speed control relay. The cooling fan speed control relay activates and provides power to the coil of the cooling fan high speed relay. The cooling fan high speed relay remains inactive because ECM terminal 15 X1 is not grounded. The cooling fan low speed relay provides power to the cooling fan motor through cooling fan terminal 2 and the internal fan resistor.

In medium speed operation, the ECM provides ground from ECM terminal 15 X1 to the cooling fan high speed relay and the cooling fan medium speed relay. The cooling fan high speed relay remains inactive because power is not provided to the coil from the cooling fan speed control relay. The cooling fan medium speed relay activates and provides power to the cooling fan motor through cooling fan terminal 3 and the internal fan resistor.

In high speed operation, the ECM provides ground from ECM terminals 15 X1 and 44 X1. As previously described, power is now provided to both cooling fan terminals 2 and 3. In addition, power and ground are now provided to the coil of the cooling fan high speed relay. The cooling fan high speed relay activates and provides power to the cooling fan motor through cooling fan terminal 4, bypassing the internal fan resistors.

Conditions for Running the DTC

* The engine is running.
* The ignition voltage is between 11-32 V.
* The ECM driver transitions from ON to OFF or from OFF to ON.

Conditions for Setting the DTC

P0480

The ECM detects an open, short to ground, or short to voltage on the Cooling Fan Relay control circuit for more than 0.5 s.

P0481

The ECM detects an open, short to ground, or short to voltage circuit on the Cooling Fan High Speed Relay or the Cooling Fan Medium Speed Relay control circuit for more than 0.5 s.

Action Taken When the DTC Sets

DTCs P0480, P0481 are Type B DTCs.

Conditions for Clearing the DTC

DTCs P0480, P0481 are Type B DTCs.

Reference Information
Schematic Reference

Engine Cooling Schematics [1][2]Electrical Diagrams
Connector End View Reference

Component Connector End Views Sunshade - Left (D6I)
Description and Operation

Cooling System Description and Operation (LDE, LLU, LXV, 2H0 LUW and LFH) Description and OperationCooling System Description and Operation (1.4L LUH, LUJ, and LUV) Description and Operation
Electrical Information Reference

* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs

Scan Tool Reference

Control Module References Control Module Referencesfor scan tool information

Circuit/System Verification

1. Ignition ON, command the Cooling Fan Relay 1 ON and OFF with a scan tool. You should hear the KR20F Cooling Fan Relay, KR20C Cooling Fan Low Speed Relay, and KR20E Cooling Fan Speed Control Relay click when commanded ON and OFF.
2. Command the Cooling Fan Relay 2 ON and OFF with a scan tool. You should hear the KR20P Cooling Fan Medium Speed Relay click when commanded ON and OFF.
3. Operate the vehicle within the conditions for running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the freeze frame/failure records data.

Circuit/System Testing

1. Ignition OFF, disconnect the KR20D Cooling Fan High Speed Relay, KR20E Cooling Fan Speed Control Relay, KR20F Cooling Fan Relay, or KR20P Cooling Fan Medium Speed Relay.
2. Ignition ON, verify that a test lamp illuminates between the KR20F Cooling Fan Relay ignition circuit terminal 85, or KR20P Cooling Fan Medium Speed Relay ignition circuit terminal 1 and ground.

• If the test lamp does not illuminate, test the KR20F Cooling Fan Relay, and the KR20P Cooling Fan Medium Speed Relay ignition circuit for a short to ground or an open/high resistance.

3. Connect a 20 A fused jumper wire between terminal 30 and terminal 87 at the KR20E Cooling Fan Speed Control Relay verify that a test lamp illuminates between KR20D Cooling Fan High Speed Relay terminal 1 and ground.

• If the test lamp does not illuminate, test the KR20D Cooling Fan High Speed Relay for an open/high resistance

4. Connect a test lamp between the KR20F Cooling Fan Relay control circuit terminal 86 and B+, or KR20D Cooling Fan High Speed Relay, or KR20P Cooling Fan Medium Speed Relay control circuit terminal 2 and B+.
5. Command the Cooling Fan Relay 1 Command, or Cooling Fan Relay 2 Command ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states for the appropriate relay.

• If the test lamp is always ON, test the KR20F Cooling Fan Relay, KR20D Cooling Fan High Speed Relay or KR20P Cooling Fan Medium Speed Relay control circuit for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module.
• If the test lamp is always OFF, test the relay control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.

6. If all circuits test normal, test or replace the KR20F Cooling Fan Relay, KR20D Cooling Fan High Speed Relay or the KR20P Cooling Fan Medium Speed Relay.

Component Testing

Relay Test
1. Ignition OFF, disconnect the KR20C Cooling Fan Low Speed Relay, KR20D Cooling Fan High Speed Relay, KR20E Cooling Fan Speed Control Relay, KR20F Cooling Fan Relay, or KR20P Cooling Fan Medium Speed Relay.
2. Measure for 70-110 ohm between terminals 85 and 86 of the KR20C Cooling Fan Low Speed Relay, KR20E Cooling Fan Speed Control Relay, KR20F Cooling Fan Relay or terminals 1 and 2 of the KR20D Cooling Fan High Speed Relay or KR20P Cooling Fan Medium Speed Relay.

• If the resistance is not within the specified range, replace the appropriate KR20C Cooling Fan Low Speed Relay, KR20D Cooling Fan High Speed Relay, KR20E Cooling Fan Speed Control Relay, KR20F Cooling Fan Relay, or KR20P Cooling Fan Medium Speed Relay.

3. Measure for infinite resistance between following terminals of the appropriate KR20C Cooling Fan Low Speed Relay, KR20D Cooling Fan High Speed Relay, KR20E Cooling Fan Speed Control Relay, KR20F Cooling Fan Relay, or KR20P Cooling Fan Medium Speed Relay:

* Terminals 30 and 86 KR20C Cooling Fan Low Speed Relay, KR20E Cooling Fan Speed Control Relay, and KR20F Cooling Fan Relay.
* Terminals 30 and 87 KR20C Cooling Fan Low Speed Relay, KR20E Cooling Fan Speed Control Relay, and KR20F Cooling Fan Relay.
* Terminals 30 and 85 KR20C Cooling Fan Low Speed Relay, KR20E Cooling Fan Speed Control Relay, and KR20F Cooling Fan Relay.
* Terminals 85 and 87 KR20C Cooling Fan Low Speed Relay, KR20E Cooling Fan Speed Control Relay, and KR20F Cooling Fan Relay.
* Terminals 3 and 2 KR20D Cooling Fan High Speed Relay and KR20P Cooling Fan Medium Speed Relay.
* Terminals 3 and 5 KR20D Cooling Fan High Speed Relay and KR20P Cooling Fan Medium Speed Relay.
* Terminals 3 and 1 KR20D Cooling Fan High Speed Relay and KR20P Cooling Fan Medium Speed Relay.
* Terminals 1 and 5 KR20D Cooling Fan High Speed Relay and KR20P Cooling Fan Medium Speed Relay.

• If continuity is detected, replace the appropriate KR20C Cooling Fan Low Speed Relay, KR20D Cooling Fan High Speed Relay, KR20E Cooling Fan Speed Control Relay, KR20F Cooling Fan Relay, or KR20P Cooling Fan Medium Speed Relay.

4. Connect a 20 A fused jumper wire from the positive terminal of the battery to the appropriate KR20C Cooling Fan Low Speed Relay, KR20E Cooling Fan Speed Control Relay, and KR20F Cooling Fan Relay terminal 86 or KR20D Cooling Fan High Speed Relay and KR20P Cooling Fan Medium Speed Relay terminal 1. Connect a jumper wire from the negative terminal of the battery to KR20C Cooling Fan Low Speed Relay, KR20E Cooling Fan Speed Control Relay, and KR20F Cooling Fan Relay terminal 85 or KR20D Cooling Fan High Speed Relay and KR20P Cooling Fan Medium Speed Relay terminal 2. Measure for less than 5 ohm between KR20C Cooling Fan Low Speed Relay, KR20E Cooling Fan Speed Control Relay, and KR20F Cooling Fan Relay terminal 30 and terminal 87 or KR20D Cooling Fan High Speed Relay and KR20P Cooling Fan Medium Speed Relay terminal 5 and terminal 3.

• If the resistance measures more than 5 ohm, replace the appropriate KR20C Cooling Fan Low Speed Relay, KR20D Cooling Fan High Speed Relay, KR20E Cooling Fan Speed Control Relay, KR20F Cooling Fan Relay, or KR20P Cooling Fan Medium Speed Relay.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

* Relay Replacement (Attached to Wire Harness) Relay Replacement (Attached to Wire Harness)Relay Replacement (Within an Electrical Center) Relay Replacement (Within an Electrical Center)
* Control Module References Control Module Referencesfor Engine Control Module replacement, programming, and setup

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