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 Instructions provides 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 switch closes allowing voltage to be supplied to the brake booster pump motor.
Reference Information
Schematic Reference
Hydraulic Brake Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
Description and Operation
Brake Assist System Description and Operation Description and Operation
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
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
Verify that a vacuum leak is not present within the power brake booster system, refer to Brake Assist System Diagnosis Component Tests and General Diagnostics.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the M9 Brake Booster Pump Motor.
2. Test for less than 5 ohms between the ground circuit terminal 1 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. 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, test or replace the M9 Brake Booster Pump Motor.
4. Ignition OFF, connect the harness connector at the M9 Brake Booster Pump Motor and disconnect the harness connector at the B19C Brake Booster Vacuum Switch.
5. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 1 and ground.
• If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
6. 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.
7. Connect a 5 A fused jumper wire between the ignition circuit terminal 1 and the control circuit terminal 2, verify the M9 Brake Booster Pump Motor activates.
• If the M9 Brake Booster Pump Motor does not activate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the M9 Brake Booster Pump Motor.
8. If all circuits test normal, test or replace the B19C Brake Booster Vacuum Switch.
Component Testing
Dynamic Test
1. Ignition OFF, disconnect the harness connector at the M9 Brake Booster Pump Motor.
2. Connect a 30 A fused jumper wire between the B+ terminal 5 and B+
3. Connect a 5 A fused jumper wire between the ignition terminal 2 and B+
4. Connect a jumper wire between the ground terminal 1 and ground, verify the M9 Brake Booster Pump Motor activates.
• If the M9 Brake Booster Pump Motor does not activate, replace the M9 Brake Booster Pump Motor.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
Power Brake Booster Pump Replacement Service and Repair