Symptom Related Diagnostic Procedures
Brake Booster Pump Motor Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructionsprovides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
The brake booster vacuum switch monitors the amount of vacuum available to the power brake booster. When the vacuum within the system drops, the switch within the brake booster vacuum sensor closes allowing voltage to be supplied to the brake booster pump relay.
Reference Information
Schematic Reference
Hydraulic Brake Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Connector End Views By Name
Description and Operation
Brake Booster Vacuum Assist Description and Operation Brake Booster Vacuum Assist
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Circuit/System Testing
1. Inspect the brake booster vacuum system for damage, leakage and correct installation.
• If damage, leakage or incorrect installation is diagnosed, repair or replace the component.
2. Ignition OFF, disconnect the X1 harness connector at the KR14 Brake Booster Pump Motor Relay.
3. Test for less than 5 ohm between the ground circuit terminal 1 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
4. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 5 and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, replace the M9 Brake Booster Pump Motor.
5. Ignition OFF, verify that a test lamp does not illuminate between the control circuit terminal 2 and ground.
• If the test lamp illuminates, test the control circuit for a short to voltage. If the circuit tests normal, replace the K17 Electronic Brake Control Module.
6. Disconnect the harness connector at the B19B Brake Booster Vacuum Sensor.
7. Test for less than 5 ohm between the low reference circuit terminal 2 and ground.
• If greater than the specified value, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K17 Electronic Brake Control Module.
8. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal 3 and ground.
• If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the K17 Electronic Brake Control Module.
• If less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K17 Electronic Brake Control Module.
9. Verify the scan tool Brake Booster Vacuum Sensor Parameter is greater than 100 kPa (14.5 PSI).
• If less than the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the K17 Electronic Brake Control Module.
10. Install a fused jumper wire between the signal circuit terminal 1 and the low reference circuit terminal 2.
11. Verify the scan tool Brake Booster Vacuum Sensor Parameter is less than 30 kPa (4 PSI).
• If greater than the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K17 Electronic Brake Control Module.
12. Ignition OFF, disconnect the X2 harness connector at the KR14 Brake Booster Pump Motor Relay.
13. Connect a 10 A fused jumper wire between KR14 Brake Booster Pump Motor Relay B+ circuit terminal 1 X2 and B+. Connect a 10 A fused jumper wire between KR14 Brake Booster Pump Motor Relay ground circuit terminal 2 X2 and ground. Verify that the M9 Brake Booster Pump Motor activates.
• If the M9 Brake Booster Pump Motor is not active, test the KR14 Brake Booster Pump Motor Relay ground circuit terminal 2 X2 and the control circuit terminal 1 X2 for an open/high resistance. If the circuit tests normal, replace the M9 Brake Booster Pump Motor.
14. Remove all fused jumper wires. Connect the KR14 Brake Booster Pump Motor Relay to the harness connector. Disconnect the harness connector at the K17 Electronic Brake Control Module. Connect a 10 A fused jumper wire between the K17 Electronic Brake Control Module circuit terminal 26 and B+.
15. Verify that the M9 Brake Booster Pump Motor activates.
• If the M9 Brake Booster Pump Motor is not active, replace the KR14 Brake Booster Pump Motor Relay.
16. If all circuits test normal, replace the K17 Electronic Brake Control Module.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Power Brake Booster Vacuum Pipe Replacement (2.4L) Power Brake Booster Vacuum Pipe Replacement (2.4L)Power Brake Booster Vacuum Pipe Replacement (3.0L, 3.6L) Power Brake Booster Vacuum Pipe Replacement (3.0L, 3.6L)
* Power Brake Booster Pump Replacement Power Brake Booster Pump Replacement