Chevrolet Trax: Fuel pump electrical circuit diagnosis (LUJ)

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.

Circuit/System Description

The engine control module (ECM) provides ignition voltage to the coil side of the fuel pump relay whenever the engine is cranking or running. The ECM enables the fuel pump relay as long as the engine is cranking or running.

Diagnostic Aids

The following conditions may cause the fuel pump fuse to open:

• The fuse is faulty.
• There is an intermittent short to ground in the supply voltage circuit of the fuel pump.
• The fuel pump has an intermittent internal condition.

Reference Information

Schematic Reference

Engine Controls Schematics (Encore) , Engine Controls 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

Description and Operation

Fuel System Description (LUJ)

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

Special Tools

J 43244 Relay Puller Pliers

For equivalent regional tools, refer to Special Tools (Diagnostic Tools) .

Circuit/System Verification

1. Ignition ON.
2. Verify the scan tool parameters listed below do not display Malfunction when commanding the Fuel Pump Relay ON and OFF.

• Fuel Pump Relay Control Circuit Low Voltage Test Status
• Fuel Pump Relay Control Circuit Open Test Status
• Fuel Pump Relay Control Circuit High Voltage Test Status
• If Malfunction is displayed

Refer to Circuit/System Testing.

• If Malfunction is not displayed

3. All OK.

Circuit/System Testing

1. Ignition OFF and all vehicle systems OFF, disconnect the KR23A Fuel Pump Relay. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 ohms between the ground circuit terminal 86 and ground.

• If 10 ohms or greater

1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 10 ohms

3. Ignition ON.
4. Verify a test lamp illuminates between the ignition circuit terminal 30 and ground.

• If the test lamp does not illuminate and the circuit fuse is OK

1. Ignition OFF, remove the test lamp.
2. Test for less than 2 ohms in the ignition circuit 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 OK 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 ignition circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance

3. Disconnect the harness connector at the G12 Fuel Pump.
4. Test for infinite resistance between the output control circuit terminal 87 and ground.

• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, test or replace the G12 Fuel Pump.
• If the test lamp illuminates

5. Verify that a test lamp does not illuminate between the control circuit terminal 85 and ground.

• If the test lamp illuminates

1. Ignition OFF, remove the test lamp, disconnect the harness connector at the K20 Engine Control Module, ignition ON.
2. Test for less than 1 V between the control circuit and ground.

• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K20 Engine Control Module.
• If the test lamp does not illuminate

6. Remove the test lamp.
7. Verify the scan tool Fuel Pump Relay Control Circuit Low Voltage Test Status parameter is OK when commanding the Fuel Pump Relay ON.

• If OK is not displayed

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Test for infinite resistance between the 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 OK is displayed

8. Install a 3 A fused jumper wire between the control circuit terminal 85 and the ground circuit terminal 86.
9. Verify the scan tool Fuel Pump Relay Control Circuit Low Voltage Test Status parameter is Malfunction when commanding the Fuel Pump Relay ON.

• If Malfunction is not displayed

1. Ignition OFF, remove the jumper wire, disconnect the harness connector at the K20 Engine Control Module.
2. Test for less than 2 ohms in the 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 Malfunction is displayed

10. Verify that a test lamp does not illuminate between the output control circuit terminal 87 and ground.

• If the test lamp illuminates

Repair the short to voltage on the control circuit

• If the test lamp does not illuminate

11. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the G12 Fuel Pump. It may take up to 2 minutes for all vehicle systems to power down.
12. Test for less than 10 ohms between the G12 Fuel Pump ground circuit terminal 2 and ground.

• If 10 ohms or greater

1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 10 ohms

13. Connect the harness connector at the G12 Fuel Pump.
14. Ignition ON, connect a 20 A fused jumper wire between the ignition circuit terminal 30 and the output control circuit terminal 87.
15. Verify the G12 Fuel Pump is activated.

• If the G12 Fuel Pump does not activate

1. Ignition OFF, remove the jumper wire, disconnect the harness connector at the G12 Fuel Pump.
2. Test for less than 2 ohms in the output 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 G12 Fuel Pump.
• If the G12 Fuel Pump activates

16. Test or replace the KR23A Fuel Pump Relay.

Component Testing

Relay Test

1. Ignition OFF, disconnect the KR23A Fuel Pump Relay.
2. Test for 70-120 ohms between terminals 85 and 86.

• If less than 70 ohms or greater than 120 ohms

Replace the KR23A Fuel Pump Relay.

• If between 70-120 ohms

3. Test for infinite resistance between the terminals listed below:

• 30 and 86
• 30 and 87
• 30 and 85
• 85 and 87
• If less than infinite resistance

Replace the KR23A Fuel Pump Relay.

• If infinite resistance

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.
5. Test for less than 2 ohms between terminals 30 and 87.

• If 2 ohms or greater

Replace the KR23A Fuel Pump Relay.

• If less than 2 ohms

6. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Fuel Tank Fuel Pump Module Replacement (AWD) , Fuel Tank Fuel Pump Module Replacement (FWD) for fuel pump replacement.
• 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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