Diagnostic Test

CHECK FOR AN ACTIVE DTC
1. Turn the ignition on.
2. With the scan tool, read and record DTCs on the repair order.
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. Wait five minutes or until red brake lamp illuminates.
7. Press and release the brake pedal.
8. With the scan tool, read ABS DTCs.
  Did the DTC return?
  
  Yes
  - Go To 2
  No
  - Check the vacuum supply line to brake booster for a pinched, cut, loose or cracked vacuum hose which could cause an intermittent condition.
  - Perform the ABS-INTERMITTENT CONDITION TEST. Refer to ABS INTERMITTENT CONDITION .
CHECK VACUUM SUPPLY LINE
1. Turn the ignition off.
2. Check the vacuum supply line to brake booster for a pinched, cut, loose or open vacuum hose.
3. Disconnect the booster vacuum supply line and attach a vacuum pressure gauge.
4. Start the engine.
  Does the vacuum fluctuate with RPM change?
  
  Yes
  - Repair as necessary.
  - Perform the ABS VERIFICATION TEST. Refer to ABS VERIFICATION TEST .
  No
  - Go To 3
CHECK FOR VACUUM PRESSURE SIGNAL CHANGE
1. Turn the ignition on.
2. Remove the Vacuum Pressure Sensor from the Booster.
3. Block off the vacuum feed port.
4. Connect a vacuum pump to the Vacuum Pressure Sensor.
5. Apply vacuum to the Vacuum Pressure Sensor.
6. Using the scan tool, and a pressure gauge watch for the signal change.
7. Using the scan tool, watch for signal change.
  Is the signal changing and does it correlate to the pressure gauge reading?
  
  Yes
  - Go To 4
  No
  - Replace the Vacuum Pressure Sensor.
  - Perform the ABS VERIFICATION TEST. Refer to ABS VERIFICATION TEST .
CHECK BRAKE BOOSTER CHECK VALVE
1. Turn the ignition off.
2. Remove the Brake Booster Check Valve.
3. Apply vacuum to the booster side of the check valve.
  Is the Brake Booster Check Valve holding vacuum?
  
  Yes
  - Replace the Brake Booster in accordance with the Service Information. Refer to BOOSTER, POWER BRAKE, REMOVAL AND INSTALLATION .
  - Perform the ABS VERIFICATION TEST. Refer to ABS VERIFICATION TEST .
  No
  - Replace Brake Booster Check Valve.
  - Perform the ABS VERIFICATION TEST. Refer to ABS VERIFICATION TEST .