Brake Booster Pump Motor Malfunction
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 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 Views)
Description and Operation
Brake Booster Vacuum Assist Description and Operation (Brake Booster Vacuum Assist 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)
Circuit/System Testing
1. Ignition OFF, disconnect the X1 harness connector at the brake booster pump relay.
2. Test for less than 1 ohm 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, replace the brake booster pump motor.
4. Disconnect the 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. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal 2 for a short to ground.
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 10 A fused jumper wire between the ignition circuit terminal 1 and the control circuit terminal 2. Verify that a test lamp illuminates between the brake booster pump relay control circuit terminal 2 X1 and ground.
• If the test lamp does not illuminate, test the control circuit for an open/high resistance.
8. Ignition OFF, connect the X1 harness connector at the brake booster pump relay. Disconnect the X2 harness connector at the brake booster pump relay. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 1 and ground circuit terminal 2 at the relay.
• If the test lamp does not illuminate, replace the brake booster pump relay.
9. Ignition OFF, connect the X2 harness connector at the brake booster pump relay. Verify the brake booster pump motor activates.
• If the brake booster pump motor does not active, replace the brake booster pump motor.
10. If all circuits test normal, test or replace the brake booster vacuum switch.
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)Power Brake Booster Vacuum Pipe Replacement (3.0L, 3.6L) (Power Brake Booster Vacuum Pipe Replacement)
* Power Brake Booster Pump Replacement (Service and Repair)