C0021

C0021-BRAKE BOOSTER PERFORMANCE





For a complete wiring diagram, refer to the Wiring Information .

- When Monitored:
With the ignition on.

- Set Condition:
When the Vacuum Pressure Sensor indicates a failure in the Vacuum Booster. After the cold start phase (i.e. 3 min after ignition-on) and if the engine is running above 600 RPM there should be at least -135 mbar (-1.958 psi) of differential pressure in the vacuum-chamber for boosting the pedal force. If the pressure remains below this value for more than A) 1 sec, if brake is applied, B) 2 min, if brake is not applied, but throttle position is below 30%, C) 10 min, if brake is not applied and throttle position is over 30%, and vehicle speed is over 1 mph (2 km/h), a booster vacuum failure is reported.





1. CHECK FOR A DTC C0021-BRAKE BOOSTER PERFORMANCE

NOTE: This DTC must be active for the results of this test to be valid.

1. Turn the ignition on.
2. With the scan tool, read and record the DTCs.
3. With the scan tool, read and record Environmental Data to help identify the conditions in which the DTC was set.
4. With the scan tool, erase the DTCs.
5. Start the engine.
6. Depress and release the brake pedal.
7. With the scan tool, read and record the DTCs.

Does the scan tool display: C0021-BRAKE BOOSTER PERFORMANCE?

Yes

- Go To 2

No

- Perform the ABS INTERMITTENT CONDITION TEST. ABS Intermittent Condition Test.

2. CHECK FOR PINCHED VACUUM SUPPLY LINE
1. Turn the ignition off.
2. Check the vacuum supply line to brake booster for a pinched, cut or open hose.

Were any problems found?

Yes

- Repair as necessary.
- Perform the ABS VERIFICATION TEST. ABS Verification Test.

No

- Go To 3

3. CHECK FOR VACUUM PRESSURE SIGNAL CHANGE
1. Turn the ignition on.
2. Remove the Vacuum Pressure Sensor from the Booster.
3. Connect a vacuum pump to the Vacuum Pressure Sensor.
4. Apply vacuum to the Vacuum Pressure Sensor and watch for signal change.

Is the voltage signal changing on the scan tool as vacuum is being applied?

Yes

- Go To 4

No

- Replace the Vacuum Pressure Sensor.
- Perform the ABS VERIFICATION TEST. ABS Verification Test.

4. CHECK BRAKE BOOSTER CHECK VALVE
1. Remove the Brake Booster Check Valve.
2. Apply vacuum to the booster side of the check valve.

Is the Brake Booster Check Valve holding vacuum?

Yes

- Replace the Brake Booster.
- Perform the ABS VERIFICATION TEST. ABS Verification Test.

No

- Replace Brake Booster Check Valve.
- Perform the ABS VERIFICATION TEST. ABS Verification Test.