Spark

Brake Booster Pump Motor Malfunction

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

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

Verify that a vacuum leak is not present within the power brake booster system, refer to Brake Assist System Diagnosis .

1. Check the F20DA fuse on the X51A instrument panel fuse block if it is normal.

⇒	If it is blown, replace the fuse.

2. Check the F9UA fuse on the X50A underbonnet fuse block if it is normal.

⇒	If it is blown, replace the fuse.

3. Check the KR14 brake booster pump motor relay on the X50A underbonnet fuse block if it is normal.

⇒	If it is inoperative, replace the relay.

4. Ignition OFF, dis the harness connector at the B19C brake booster vacuum switch.
5. Ignition ON, verify that a test lamp illuminates between the brake booster vacuum switch ignition circuit terminal 1 and ground.

⇒	If the test lamp does not illuminate, test the brake booster vacuum switch ignition circuit for a short to ground or an open/high resistance.

6. Ignition Off, test for less than 1 ohm between terminal 2 of the B19C brake booster vacuum switch and terminal 85 of the KR14 brake booster pump motor relay.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

7. Test for less than 1 ohm between the ground circuit terminal 86 of the brake booster pump motor relay and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

8. Ignition ON, with the power vacuum brake booster vacuum reserve depleted, check if the KR14 brake booster pump motor relay is activated.

⇒	If the KR14 brake booster pump motor relay is not active, replace the B19C brake booster vacuum switch.

9. Ignition OFF, disconnect the harness connector at the M9 brake booster pump motor.
10. Test for less than 1 ohm between the ground circuit terminal 2 and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

11. With ignition ON and the power vacuum brake booster vacuum reserve depleted, verify that a test lamp illuminates between the B+ circuit terminal 1 and ground.

⇒	If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

12. If all circuits test normal, test or replace the M9 brake booster pump motor.

1. Ignition OFF, disconnect the harness connector at the M9 brake booster pump motor.
2. Connect a 30A fused jumper wire between the B+ terminal 1 and B+.
3. Connect a jumper wire between the ground terminal 2 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.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.