Diagnostic Test

1. Perform any Service Bulletins that may apply.
2. Turn the ignition on.
3. With the scan tool, read ABS DTCs and record on the repair order.
4. With the scan tool, read and record Environmental Data to help identify the conditions in which the DTC was set.
5. With the scan tool, erase ABS DTCs.
6. Turn the ignition off.
7. Start the Vehicle.
8. Press the brake pedal firmly and release three times, holding for two seconds each time.
9. With the scan tool, read ABS DTCs.

   Is the DTC active?

   Yes 

   • Go To  2

   No 

   • The condition that caused the symptom is currently not present. Inspect the related wiring for a possible intermittent condition. Look for any chafed, pierced, pinched, or partially broken wires.
   • Perform the ABS-INTERMITTENT CONDITION TEST. Refer to ABS INTERMITTENT CONDITION .

1. Start the engine.
2. With the scan tool, under "Data Display" view and record the vacuum pressure signal with no brake applied.
3. Turn the engine off.
4. Turn the ignition on.
5. With the scan tool, under "Data Display" view and record the vacuum pressure with no brake applied.

   Is the vacuum pressure signal staying consistent?

   Yes 

   • Go To  3

   No 

   • Go To  4

1. Start the engine.
2. Measure the vacuum pressure while pressing the brake pedal rapidly several times.
3. Turn the engine off.
4. Turn the ignition on.

   Does the vacuum drop below 50 mbar (7 psi)?

   Yes 

   • Go To  5

   No 

   • Perform the ABS-INTERMITTENT CONDITION TEST. Refer to ABS INTERMITTENT CONDITION .

1. The ignition must be off when checking the continuity of a circuit.
2. Isolate the circuit by disconnecting the ABS Module harness connector and the Vacuum Pressure Sensor harness connector containing the circuit being tested. Note:  Use the wiring diagram as a guide to follow the path of the circuit.
3. Before measuring the resistance of any circuit, first measure the resistance between the two leads of the DVOM. Note:  The meter leads can add resistance to the measurement value.
4. Connect one lead of the DVOM to the circuit being tested at the Vacuum Pressure Sensor harness connector.
5. Connect the other lead to the circuit being tested at the ABS Module harness connector and measure the resistance of the circuit.

Is the resistance below 3.0 Ohms?

Yes 

• Go To  5

No 

• Repair the circuit for an open/high resistance.
• Perform the ABS VERIFICATION TEST. Refer to ABS VERIFICATION TEST .

1. Turn the ignition on.
2. Remove the Vacuum Pressure Sensor from the Brake Booster.
3. Connect a vacuum pump to the Vacuum Pressure Sensor.
4. Apply vacuum to the Vacuum Pressure Sensor.
5. With the scan tool, under "Data Display" view the vacuum pressure and watch for signal change.

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

   Yes 

   • Go To  6

   No 

   • Replace the Vacuum Pressure Sensor.
   • Perform the ABS VERIFICATION TEST. Refer to ABS VERIFICATION TEST .

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 

   • Go To  7

   No 

   • Replace the Brake Booster Check Valve.
   • Perform the ABS VERIFICATION TEST. Refer to ABS VERIFICATION TEST .

1. Install the Brake Booster Check Valve.
2. Connect a vacuum pump to the Brake Booster Check Valve.
3. Using the vacuum pump, apply vacuum to the Brake Booster.

   Is the Power Brake Booster holding vacuum?

   Yes 

   • Go To  8

   No 

   • Replace the Power 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 .

1. Verify the vehicle is equipped with an electric vacuum pump.

   Is the vehicle is equipped with a electric vacuum pump?

   Yes 

   • Replace the Electric Vacuum Pump in accordance with the Service Information. Refer to PUMP, ELECTRIC VACUUM, REMOVAL AND INSTALLATION .
   • Perform the ABS VERIFICATION TEST. Refer to ABS VERIFICATION TEST .

   No 

   • Go To  9

1. Turn the ignition off.
2. Replace the Vacuum Pressure Sensor.
3. Perform the ABS VERIFICATION TEST. Refer to ABS VERIFICATION TEST .
4. With the scan tool, read the DTCs.

   Does the DTC remain active?

   Yes 

   • Go To  10

   No 

   • Test complete, the condition or conditions that originally set this DTC are not present at this time.

1. Disconnect the ABS Module harness connector.
2. Disconnect all related in-line harness connections (if equipped).
3. Disconnect the related component harness connectors.
4. Inspect harness connectors, component connectors, and all male and female terminals for the following conditions:
   • Proper connector installation.
   • Damaged connector locks.
   • Corrosion.
   • Other signs of water intrusion.
   • Weather seal damage (if equipped).
   • Bent terminals.
   • Overheating due to a poor connection (terminal may be discolored due to excessive current draw).
   • Terminals that have been pushed back into the connector cavity.
   • Perform a terminal drag test on each connector terminal to verify proper terminal tension.

   Repair any conditions that are found.

5. Connect the ABS Module harness connector. Be certain that the harness connector is fully seated and the connector lock is fully engaged.
6. Connect all in-line harness connectors (if equipped). Be certain that all connectors are fully seated and the connector locks are fully engaged.
7. Connect the related component harness connectors. Be certain that all connectors are fully seated and the connector locks are fully engaged.
8. With the scan tool, erase DTCs.
   WARNING:

   To avoid possible serious or fatal injury, check brake capability is available before road testing.

9. Using the recorded Event and Environmental Data, along with the When Monitored and Set Conditions above, operate the vehicle in the conditions that set the DTC.
10. With the scan tool, read ABS Module DTCs.

    Did the DTC return?

    Yes 

    • Replace the Anti-lock Brake System (ABS) Module in accordance with the Service Information. Refer to MODULE, ANTI-LOCK BRAKE SYSTEM (ABS), REMOVAL AND INSTALLATION .
    • Perform ABS VERIFICATION TEST. Refer to ABS VERIFICATION TEST .

    No 

    • Perform ABS VERIFICATION TEST. Refer to ABS VERIFICATION TEST .
    • Test complete.