Chevrolet Trax: Cooling fan always on  (LUJ OR LUV)

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 the diagnostic category.

Circuit/System Description

The engine cooling fan system is composed of one cooling fan, a series of 5 relays, the engine control module (ECM), and the associated wiring. The cooling fan assembly includes two resistors. This combination of components enables the ECM to operate the cooling fan at 3 speeds using two fan control circuits.

Diagnostic Aids

• The scan tool cooling fan output control operates as follows:

• Cooling Fan Relay 1 operates the fan at a low speed
• Cooling Fan Relay 2 and 3 operates the fan at a medium speed
• Cooling Fan Relay 1, 2 and 3 operates the fan at a high speed

• Certain resistance conditions with intake air temperature (IAT) or engine coolant temperature (ECT) sensors may cause unwarranted cooling fan activation. If the ECM is commanding the cooling fans ON for no apparent reason and without any component or system DTCs set, the IAT or ECT sensor may be skewed. If this condition is suspected, refer to the Temperature Versus Resistance tables in Specifications of the appropriate engine controls subsection.
• If the cooling fan operates at high speed when the ECM is requesting medium speed operation, test or replace the KR20E Cooling Fan Speed Control Relay.

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)

Electrical Information Reference

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

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. Ignition ON.
2. Verify that there are no cooling system DTCs set.

• If any DTCs are set

Refer to Diagnostic Trouble Code (DTC) List - Vehicle .

• If no DTCs are set

3. Verify the scan tool parameters listed below display OFF.

• Cooling Fan Relay 1 Command
• Cooling Fan Relays 2 and 3 Command
• If a scan tool parameter displays ON

Refer to Diagnostic Aids and Symptoms - Engine Cooling for further diagnosis

• If both scan tool parameters display OFF

4. Verify that the fan is not activated.

• If the fan is operating

Refer to Circuit/System Testing.

• If the fan is OFF

5. All OK.

Circuit/System Testing

NOTE: The following tests must be performed on each cooling fan relay.

1. Ignition OFF, disconnect each cooling fan relay one at a time, in the order listed below, ignition ON:

• KR20F Cooling Fan Relay
• KR20C Cooling Fan Low Speed Relay
• KR20P Cooling Fan Medium Speed Relay
• KR20D Cooling Fan High Speed Relay

2. Verify that the cooling fan is not activated after each relay is removed.

• If the cooling fan is ON with all of the listed relays removed

1. Ignition OFF, disconnect the harness connector at the R10 Cooling Fan Resistor, ignition ON.
2. Test for less than 1 V between the relay controlled output circuit terminal listed below and ground:

• KR20C Cooling Fan Low Speed Relay terminal 87/5
• KR20P Cooling Fan Medium Speed Relay terminal 87/5
• KR20D Cooling Fan High Speed Relay terminal 87/5
• If 1 V or greater, repair the short to voltage in the appropriate circuit.
• If the cooling fan is OFF after a listed relay is removed

3. 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 or greater than the specified range

Replace the cooling fan relay.

• If within the specified range

4. Test for infinite resistance between the 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 diagnostic procedure.

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

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