Chevrolet Trax: DTC P0480 OR P0481 (2H0): Cooling fan relay 1/2 control circuit

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• 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 cooling fan system is composed of one cooling fan, 2 relays, the engine control module (ECM), and the associated wiring. The cooling fan assembly includes 1 resistor mounted in the cooling fan shroud. This combination of components enables the ECM to operate the cooling fan at 2 speeds using two fan control circuits. The ECM activates the applicable relay by grounding the control circuit with a solid state device called a driver. Each driver is equipped with a feedback circuit that is pulled-up to a voltage. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage. The ECM will operate the cooling fan at either Low or High speed based on the cooling requirements.

Conditions for Running the DTC

• The ignition voltage is 11-18 volts.
• The engine speed is 400 RPM or greater.
• The ECM has commanded the output driver ON and OFF at least once during the ignition cycle.
• The DTCs 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 for greater than 5 seconds.

Action Taken When the DTC Sets

DTCs P0480 and P0481 are Type C DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0480 and P0481 are Type C 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:

• Cooling Fan Relay 1 operates the fan at low speed
• Cooling Fan Relay 2 operates the fan at a high speed

• When disconnecting or removing fuses and relays from a fuse block, always inspect the component electrical terminals for corrosion and the correct orientation in the fuse block. Test the mating electrical terminals for tightness.

Reference Information

Schematic Reference

Engine Heating/Cooling Schematics (Encore), Engine Heating/Cooling Schematics (Trax)

Connector End View Reference

WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - ENCORE WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - TRAX

Electrical Information Reference

• Electrical Center Identification Views (Encore) , Electrical Center Identification Views (Trax)

Description and Operation

Cooling Fan Description and Operation (LUJ or LUV), Cooling Fan Description and Operation (2H0)

Electrical Information Reference

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

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (LUV)

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. Ignition ON.
2. Verify an audible click is heard or felt from each cooling fan relay when commanding the cooling fan ON and OFF with a scan tool.

• If a click is not heard or felt at each of the relays

Refer to Circuit/System Testing.

• If a click is heard or felt at each of the relays

3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
4. Verify the DTC does not set.

• If the DTC sets

Refer to Circuit/System Testing.

• If the DTC does not set

5. All OK.

Circuit/System Testing

1. Ignition OFF, disconnect the cooling fan relays listed below:

• KR20C Cooling Fan Low Speed Relay
• KR20D Cooling Fan High Speed Relay

NOTE:

The following test must be performed on each of the relay coil ignition circuits.

2. Ignition ON, verify that a test lamp illuminates between the relay coil ignition circuit terminal listed below and ground:

• KR20C Cooling Fan Low Speed Relay terminal 85
• KR20D Cooling Fan High Speed Relay terminal 85
• If the test lamp does not illuminate and the circuit fuse is good

1. Ignition OFF, remove the test lamp.
2. Test for less than 2 ohms in the ignition circuit of the appropriate cooling fan relay, end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.
• If the test lamp does not illuminate and the circuit fuse is open

1. Ignition OFF, remove the test lamp.
2. Test for infinite resistance between the relay coil ignition circuits listed below and ground:

• KR20C Cooling Fan Low Speed Relay terminal 85
• KR20D Cooling Fan High Speed Relay terminal 85

• If less than infinite resistance, repair the short to ground in the circuit.
• If infinite resistance, test all of the appropriate relays for a shorted condition and replace as necessary.
• If the test lamp illuminates

3. Ignition OFF, remove the test lamp, ignition ON.

NOTE: The following tests must be performed on the two fan relay control circuits.

4. Connect a DMM, set on the diode setting, between a control circuit terminal listed below and ground:

• KR20C Cooling Fan Low Speed Relay terminal 86
• KR20D Cooling Fan High Speed relay terminal 86

5. Verify the DMM reading is greater than 2.5 V or displays O.L.

• If 2.5 V or less

1. Ignition OFF, disconnect the X1 harness connector at the K20 Engine Control Module.
2. Test for infinite resistance between the appropriate relay coil control circuit and ground

• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the K20 Engine Control Module.
• If greater than 2.5 V or displays O.L.

NOTE: The following test must be performed on the two fan relay circuits.

6. Verify the DMM reading is less than 1 V when commanding the Cooling Fan Relays ON with a scan tool.

• If 1 V or greater

1. Ignition OFF, disconnect the X1 harness connector at the K20 Engine Control Module, ignition ON.
2. Test for less than 1 V between the appropriate cooling fan relay control circuit and ground.

• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V.

3. Ignition OFF.
4. Test for less than 2 ohms in the appropriate cooling fan relay control circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K20 Engine Control Module.
• If less than 1 V

7. Test or replace the appropriate cooling fan relay.

Component Testing

1. Ignition OFF.
2. Disconnect a cooling fan relay.
3. Test for 70-110 ohms between terminals 85/2 and 86/1.

• If less than 70 ohms or greater than 110 ohms

Replace the cooling fan relay.

• If between 70-110 ohms

4. Test for infinite resistance between following terminals:

• 30/3 and 86/1
• 30/3 and 87/5
• 30/3 and 85/2
• 85/2 and 87/5
• If less than infinite resistance

Replace the cooling fan relay.

• If infinite resistance

5. Install a 20 A fused jumper wire between relay terminal 85/2 and 12 V.
6. Install a jumper wire between relay terminal 86/1 and ground.
7. Test for less than 2 ohms between terminals 30/3 and 87/5.

• If 2 ohms or greater

Replace the cooling fan relay.

• If less than 2 ohms

8. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Relay Replacement (Within an Electrical Center) , Relay Replacement (Attached to Wire Harness)
• Control Module References for ECM replacement, programming, and setup

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