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P0480




DTC P0480 or P0481

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

Diagnostic Fault Information






Circuit/System Description

The engine control module (ECM) commands the fan ON in either high speed or low speed, depending on cooling requirements.

In low speed operation, the ECM supplies a ground to the coil side of the low speed fan relay. This energizes the coil and applies voltage directly to the cooling fan through the switch side of the low relay. The fan is connected in series to the cooling fan resistor causing the fan to operate at low speed.

In high speed operation, the ECM supplies a ground to the coil side of the fan high or fan control relay. When energized, the fan high or control relay applies voltage directly to the cooling fan through the switch side of the relay. The ECM commands the low speed fan relay OFF and the cooling fan receives full voltage and operates at high speed.

Conditions for Running the DTC

* The engine is running.

* The ignition voltage is between 11-32 V.

* The engine speed is greater 400 RPM.

* These DTCs run continuously once the above conditions are met.

Conditions for Setting the DTC

The ECM detects that the commanded state of the driver and the actual state of the control circuit do not match for greater than 2 s.

Action Taken When the DTC Sets

DTCs P0480 and P0481 are Type B DTCs.

Conditions for Clearing the DTC

DTCs P0480 and P0481 are Type B DTCs.

Reference Information

Schematic Reference

Engine Cooling Schematics [1][2]Cooling System

Connector End View Reference

Component Connector End Views Fuel Pump and Level Sensor Assembly

Description and Operation

Cooling System Description and Operation 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 References for scan tool information

Circuit/System Verification

1. Ignition ON, command the appropriate KR20C Cooling Fan Low Speed Relay, or KR20D Cooling Fan High Speed Relay ON and OFF with a scan tool. You should hear the relay click when commanded ON and OFF.

2. 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 KR20C Cooling Fan Low Speed Relay, and KR20D Cooling Fan High Speed Relay.

2. Ignition ON, verify that a test lamp illuminates between the KR20C Cooling Fan Low Speed Relay, or KR20D Cooling Fan High Speed Relay coil ignition circuit terminal 86 and ground.

If the test lamp does not illuminate, test the KR20C Cooling Fan Low Speed Relay, or KR20D Cooling Fan High Speed Relay coil ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the fuse F45UA is open, test all components connected to the ignition circuit and repair and replace as necessary.

3. Connect a test lamp between the KR20C Cooling Fan Low Speed Relay, and KR20D Cooling Fan High Speed Relay coil control circuit terminal 85 and B+.

4. Command the Cooling Fan Relay 1 Command, 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 KR20C Cooling Fan Low Speed Relay, and KR20D Cooling Fan High Speed Relay coil 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 coil control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.

5. If all circuits test normal, test or replace the KR20C Cooling Fan Low Speed Relay, or KR20D Cooling Fan High Speed Relay.

Component Testing

Relay Test

1. Ignition OFF, disconnect the applicable relay.

2. Test for 70-110 ohms between terminals 85 and 86 of the relay.

If the resistance is not within the specified range, replace the relay.

3. Measure for infinite resistance between following terminals.

* Terminals 30 and 86

* Terminals 30 and 87

* Terminals 30 and 85

* Terminals 85 and 87

If not the specified value, replace the relay

4. Install a 20 A fused jumper wire between relay terminal 85 and 12 V. Install a jumper wire between relay terminal 86 and ground. Test for less than 5 ohms between terminals 30 and 87.

If greater than the specified value, replace the relay

Repair Instructions

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

* Relay Replacement (Within an Electrical Center) Relay Replacement (Within an Electrical Center)Relay Replacement (Attached to Wire Harness) Relay Replacement (Attached to Wire Harness)

* Control Module References Control Module References for Engine Control Module replacement, programming, and setup