Chevrolet Trax: Brake booster pump motor malfunction (WITH J41)

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.

Diagnostic Fault Information

Circuit/System Description

When the vacuum within the brake booster system becomes low, the brake booster vacuum switch closes and turns on the brake booster pump motor by providing battery voltage to the brake booster pump motor relay. The relay activates and supplies the voltage to the brake booster pump motor.

Reference Information

Schematic Reference

Hydraulic Brake Schematics (Encore), Hydraulic Brake 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

Brake Booster Vacuum Assist Description and Operation

Electrical Information Reference

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

Scan Tool Reference

Control Module References

Circuit/System Verification

1. Ignition ON.
2. Deplete the vacuum in the brake booster and verify the M9 Brake Booster Pump Motor turns ON

If the M9 Brake Booster Pump Motor does not turn ON

Refer to Circuit/System Testing.

If the M9 Brake Booster Pump Motor turns ON

3. Verify that the brake booster vacuum system has no damage, leakage or incorrect installation.

If damage, leakage or incorrect installation is found

Refer to Brake Assist System Diagnosis.

If the inspection is OK

4. All OK.

Circuit/System Testing

1. Ignition OFF and all vehicle systems OFF, disconnect the KR14 Brake Booster Pump Motor Relay. It may take up to 2 min for all vehicle systems to power down.
2. Test for less than 10 ohms between the ground circuit terminal 1 (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 B+ circuit terminal 3 (30) and ground.

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

1. Ignition OFF.
2. Test for less than 2 ohms in the B+ 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 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.
2. Test for infinite resistance between the B+ circuit and ground.

• 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.
2. Test for infinite resistance between the B+ circuit and ground.

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

3. Disconnect the M9 Brake Booster Pump Motor.
4. Test for infinite resistance between the control circuit terminal 5 (87) and ground.

• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the KR14 Brake Booster Pump Motor Relay.

If the test lamp illuminates

5. Ignition OFF, disconnect the B19C Brake Booster Vacuum Switch, ignition ON.
6. Verify a test lamp illuminates between ignition circuit terminal 1 and ground.

If the test lamp does not illuminate and the circuit fuse is good

1. Ignition OFF.
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 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.
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. Test for infinite resistance between the B19C Brake Booster Vacuum Switch terminal 2 and ground.

• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the KR14 Brake Booster Pump Motor Relay.

If the test lamp illuminates

7. Connect a test lamp between the KR14 Brake Booster Pump Motor Relay control circuit terminal 2 (85) and the ground circuit terminal 1 (86).

If the test lamp illuminates

Repair the short to voltage on the control circuit

If the test lamp does not illuminate

8. Ignition OFF, connect the B19C Brake Booster Vacuum Switch. Remove the vacuum hose from the brake booster to deplete the vacuum in the system, ignition ON. Verify the test lamp illuminates

If the test lamp does not illuminate

1. Ignition OFF, disconnect the harness connector at the B19C Brake Booster Vacuum Switch.
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 B19C Brake Booster Vacuum Switch.

If the test lamp illuminates

9. Verify that a test lamp does not illuminate between the relay control circuit terminal 5 (87) and ground.

If the test lamp illuminates

Repair the short to voltage on the control circuit

If the test lamp does not illuminate

10. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the M9 Brake Booster Pump Motor. It may take up to 2 min for all vehicle systems to power down.
11. Test for less than 10 ohms between the M9 Brake Booster Pump Motor ground circuit terminal 2 and ground

If 10 ohms or greater

1. 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

12. Connect the harness connector at the M9 Brake Booster Pump Motor.
13. Ignition ON, connect a 30 A fused jumper wire between the B+ circuit terminal 3 (30) and the control circuit terminal 5 (87).
14. Verify the M9 Brake Booster Pump Motor is activated.

If the M9 Brake Booster Pump Motor does not activate

1. Ignition OFF, disconnect the harness connector at the M9 Brake Booster Pump Motor.
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 M9 Brake Booster Pump Motor.

If the M9 Brake Booster Pump Motor activates

15. Test or replace the KR14 Brake Booster Pump Motor Relay.

Component Testing

Motor Test

1. Ignition OFF, disconnect the harness connector at the M9 Brake Booster Pump Motor. Install a 30 A fused jumper wire between the B+ circuit terminal 1 and B+. Install a jumper wire between the ground circuit terminal 2 and ground.
2. Verify the M9 Brake Booster Pump Motor activates.

If the brake booster pump motor does not activate

Replace the M9 Brake Booster Pump Motor.

If the brake booster pump motor activates

3. All OK.

Relay Test

1. Ignition OFF, disconnect the KR14 Brake Booster Pump Motor Relay.
2. Test for 60-180 ohms between terminals 1 and 2.

If less than 60 or greater than 180 ohms

Replace the relay.

If between 60-180 ohms

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

• 30 and 86
• 30 and 85
• 30 and 87
• 85 and 87

If less than infinite resistance

Replace the 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 relay.

If less than 2 ohms

6. 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) .
• Power Brake Booster Pump Replacement .

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