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With HP2




DTC P0480, P0481, or P0482 (with HP2)

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 Instructions) provides an overview of each diagnostic category.

DTC Descriptors
DTC P0480
- Cooling Fan Relay 1 Control Circuit

DTC P0481
- Cooling Fan Relay 2 Control Circuit

DTC P0482
- Cooling Fan Relay 3 Control Circuit

Diagnostic Fault Information





Typical Scan Tool Data









Circuit/System Description

The hybrid engine cooling fan system consists of two electrical cooling fans, two resistors, three engine control module (ECM) fan control circuits, and five fan relays. The relays are arranged in a series/parallel configuration that allows the ECM to operate the fans at low, medium, or high speed depending on cooling requirements. The ECM controls the five relays by grounding the relay control circuits.

To operate the fans, the ECM activates the applicable relay by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage. When the ECM is commanding a fan relay ON, the voltage of the control circuit should be low, near 0 volts. When the ECM is commanding a fan relay OFF, the voltage of the control circuit should be high, near battery voltage.

Conditions for Running the DTC

* The ignition voltage is between 11-32 volts.
* The engine speed is greater than 0 RPM.
* DTC P0480, P0481, and P0482 run continuously when the conditions above are met.

Conditions for Setting the DTC

* The commanded state of the ECM driver and the actual state of the control circuit do not match.
* The condition exists for greater than 5 seconds.

Action Taken When the DTC Sets

DTCs P0480, P0481 and P0482 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0480, P0481 and P0482 are Type B DTCs.

Diagnostic Aids

* The ECM has the capability of providing command to the fan relays even when a scan tool output control is being used. Always refer to the fan control command parameters on the scan tool to know which fans are being commanded ON by the ECM.
* The scan tool cooling fan output control operates as follows:

- Fan Relay 1 operates both fans at a low speed.
- Fan Relay 2 operates both fans at medium speed.
- Fan Relays 1, 2, and 3 operates both fans at high speed.

Reference Information
Schematic Reference

Engine Cooling Schematics (Diagrams)
Connector End View Reference

* Component Connector End Views (Connector End Views By Name)
* Powertrain Component Views (Powertrain Component Views)
* Electrical Center Identification Views (Application and ID)

Description and Operation

Cooling Fan Description and Operation (Gas) (Description and Operation)Cooling Fan Description and Operation (Diesel) ()
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)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference

Control Module References (Control Module References)

Circuit/System Verification

1. Engine operating, observe the DTC information with a scan tool. DTC P0480, P0481, or P0482 should not be set.
2. Command the cooling fans ON and OFF at high speed while observing the scan tool circuit test status parameters listed below:

* FC Relay 1 Ckt Open, Short Gnd, and Short Volts Test Status
* FC Relay 2 Ckt Open, Short Gnd, and Short Volts Test Status
* FC Relay 3 Ckt Open, Short Gnd, and Short Volts Test Status
The parameters should display OK or Not Run in each of the commanded states.

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, open the hood to disable the Auto-Stop function.
2. Ignition ON, verify the scan tool hood position parameter displays Open.

• If the hood position does not display Open, refer to DTC P254F (P254F).

3. Ignition OFF, disconnect all 5 cooling fan relays.
4. Ignition ON, verify that a test lamp illuminates between ground and the ignition circuit terminal of each relay listed below:

* FAN LO Relay terminal 85
* FAN MID 1 Relay terminal 85
* FAN CNTRL Relay terminal 86
* FAN MID 2 Relay terminal 86
* FAN HI Relay terminal 86

• If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test all the components connected to the ignition voltage circuit and replace as necessary.

5. Set the DMM on the diode setting. Connect the black lead to ground. Connect the red lead of the DMM to a control circuit terminal listed below:

* FAN LO Relay terminal 86
* FAN MID 1 Relay terminal 86
* FAN CNTRL Relay terminal 85
* FAN MID 2 Relay terminal 85
* FAN HI Relay terminal 85
The DMM should display OL.

• If less than the specified range, test the appropriate relay coil control circuit for a short to ground. If the circuit tests normal, replace the K20 ECM.

6. Command the appropriate cooling fan relay ON and OFF with a scan tool. The DMM should transition from OL when commanded OFF to less than 1 V when commanded ON.

• If the circuit voltage does not correspond to the specified values, test the control circuit for an open/high resistance or for a short to voltage. If the circuit tests normal, replace the K20 ECM.

7. If all circuits test normal, test or replace the appropriate KR20 relay.

Component Testing

1. Ignition OFF, disconnect the KR20 cooling fan relay.
2. Test for 50-90 ohm between terminals 85 and 86.

• If not within the specified range, replace the KR20 cooling fan relay.

3. Measure the resistance between the terminals listed below:

* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87
The DMM should display OL.

• If less than the specified range, replace the KR20 cooling fan relay.

4. Test the KR20E Fan Control Relay for less than 2 ohm between terminals 30 and 87A.

• If greater than the specified range, replace the KR20E cooling fan relay.

5. Connect a 20 A fused jumper wire between relay terminal 85 and B+. Connect a jumper wire between relay terminal 86 and ground. Test for less than 2 ohm between terminals 30 and 87.

• If greater than the specified range, replace the KR20 cooling fan 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))
* Underhood Electrical Center or Junction Block Replacement (Underhood Electrical Center or Junction Block Replacement)
* Engine Coolant Fan Replacement (Non-HP2) (Service and Repair)
* Control Module References (Control Module References) for ECM replacement, setup and programming

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