Hydraulic Brake Booster Pump

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 electronic brake control module monitors the control circuit of the brake booster pump relay. The electronic brake control module supplies ground through the pump relay control circuit which then supplies B+ voltage to actuate the brake booster pump. B+ voltage is supplied at all times to the coil side of the pump relay.

Reference Information

Schematic Reference

Hydraulic Brake Schematics

Connector End View Reference

Component Connector End Views

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 for scan tool information

Circuit/System Verification

1. Ignition ON.
2. Verify the brake booster pump motor turns ON and OFF when commanding the brake booster electric vacuum pump ON and OFF with a scan tool.


• If the brake booster pump motor does not turn ON and OFF
  Refer to Circuit/System Testing.



• If the brake booster pump motor turn ON and OFF


3. All OK.

Circuit/System Testing

1. Ignition OFF, disconnect the KR14 Brake Booster Pump Motor Relay, ignition ON.
2. Verify that a test lamp illuminates between the B+ circuit terminal 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 Ω in the B+ circuit end to end.


• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, 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. Ignition OFF, disconnect the harness connector at the G6 Brake Booster Pump-Auxillary.
4. Test for infinite resistance between the 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 G6 Brake Booster Pump-Auxillary.




• If the test lamp illuminates


3. Verify that a test lamp illuminates between the B+ circuit terminal 85 and ground.


• If the test lamp does not illuminate
  Test or replace the X50A Fuse Block-Underhood



• If the test lamp does illuminates


4. Test for less than 1 V between the control circuit terminal 87 and ground.


• If 1 V or greater
  Repair the short to voltage on the circuit.



• If less than 1 V


5. Ignition OFF, disconnect the harness connector at the G6 Brake Booster Pump-Auxillary.
6. Test for less than 10 Ω between the G6 Brake Booster Pump-Auxillary ground circuit terminal 2 and ground.


• If 10 Ω or greater


1. Test for less than 2 Ω in the ground circuit end to end.


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



• If less than 10 Ω


7. Connect the harness connector at the G6 Brake Booster Pump-Auxillary.
8. Ignition ON, connect a 20 A fused jumper wire between the KR14 Brake Booster Pump Motor Relay B+ circuit terminal 30 and the control circuit terminal 87.
9. Verify the G6 Brake Booster Pump-Auxillary activates.


• If the G6 Brake Booster Pump-Auxillary does not activate


1. Ignition OFF, remove the jumper wire, disconnect the harness connector at the G6 Brake Booster Pump-Auxillary.
2. Test for less than 2 Ω in the control circuit end to end.


• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, test or replace the G6 Brake Booster Pump-Auxillary.




• If the G6 Brake Booster Pump-Auxillary activates


10. Ignition OFF, connect the KR14 Brake Booster Pump Motor Relay. Disconnect the harness connector at the K17 Electronic Brake Control Module, ignition ON.
11. Verify the G6 Brake Booster Pump-Auxillary is not activated.


• If the G6 Brake Booster Pump-Auxillary is activated


1. Ignition OFF, disconnect the KR14 Brake Booster Pump Motor Relay.
2. Test for infinite resistance between the control circuit terminal 36 and ground.


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




• If the G6 Brake Booster Pump-Auxillary is not activated


12. Connect a 3 A fused jumper wire between the control circuit terminal 36 and ground.
13. Verify the G6 Brake Booster Pump-Auxillary activates.


• If the G6 Brake Booster Pump-Auxillary does not activate


1. Ignition OFF, remove the jumper wire, disconnect the KR14 Brake Booster Pump Motor Relay, ignition ON.
2. Test for less than 1 V between the control circuit terminal 86 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 Ω in the control circuit end to end.


• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, test or replace the KR14 Brake Booster Pump Motor Relay.




• If the G6 Brake Booster Pump-Auxillary activates


14. Test or replace the K17 Electronic Brake Control Module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Electrical Relay Replacement
• Control Module References for Engine Control Module replacement, programming and setup.