Visual Inspection and Diagnostic Pre-checks

• Make sure the stoplamp switch electrical connector is connected and free of corrosion and other contaminants.
• Make sure the stoplamp switch is installed correctly.
• Make sure the stoplamp switch operates correctly.

Harness Side

1. AC1: CHECK FOR ABS MODULE DTCS 
   • Ignition ON, engine OFF.
   • Carry out the ABS self-test.
   • Are any lost communication with PCM, invalid data from PCM, pressure sensor, wheel speed sensor or stability control sensor DTCs present in the ABS module? 

     Yes	No
     DIAGNOSE all lost communication with PCM, invalid data from PCM, pressure sensor, wheel speed sensor or stability control sensor DTCs before diagnosing DTC C0040:xx or C0044:xx. REFER to the ABS Module DTC Chart .	Go to  AC2.

2. AC2: CHECK THE PCM FOR DTCS 
   • Carry out the PCM KOEO self-test.
   • Are any DTCs present? 

     Yes	No
     DIAGNOSE all PCM DTCs before diagnosing DTC C0040:xx or C0044:xx. REFER to the applicable Electronic Engine Controls article. If the scan tool cannot communication with the PCM, DIAGNOSE the no communication concern. Refer to Module Communications Network article.	Go to  AC3.

3. AC3: CHECK THE BPP SWITCH AND BRAKE PEDAL ASSEMBLY INSTALLATION 
   • Inspect the BPP switch and brake pedal assembly. Verify there is no brake pedal pressure unintentionally applied due to incorrect BPP switch or brake pedal installation.
     • For BPP (stoplamp) switch installation, refer to Exterior Lighting article
     • For brake pedal installation, refer to Hydraulic Brake Actuation article
   • Is the stoplamp switch and brake pedal assembly installed correctly? 

     Yes	No
     Go to  AC4.	REINSTALL the brake pedal assembly or BPP switch correctly. REFER to Hydraulic Brake Actuation article or Exterior Lighting article.

4. AC4: CHECK THE PCM BPP (BOO1) PID 
   • Ignition ON, engine OFF.
   • Access the PCM and monitor the BOO1 (MODE) PID.
   • Apply and release the brake pedal.
   • Does the PID reflect the brake pedal movement? 

     Yes	No
     Go to  AC5.	DIAGNOSE the stoplamps. Refer to Exterior Lighting article

5. AC5: CHECK THE ABS MODULE BRAKE PRESSURE PID 
   • Access the ABS and monitor the BRKHYDPRESS (PRESS) PID.
   • Apply and release the brake pedal.
   • Does the PID read approximately 0 PSI with the brake pedal released and then increase when the brake pedal is applied? 

     Yes	No
     Go to  AC6.	Go to PINPOINT TEST Y .

6. AC6: CHECK THE ABS MODULE BRAKE ON/OFF (BOO_ABS) PID 
   • Access the ABS and monitor the BOO_ABS (MODE) PID.
   • Apply and release the brake pedal.
   • Does the PID reflect the brake pedal movement? 

     Yes	No
     The system is operating correctly at this time. The DTC may have been set due to high network traffic or an intermittent fault condition.	Go to  AC7.

7. AC7: CHECK FOR CORRECT ABS MODULE TO HCU FASTENER TORQUE VALUES 
   NOTE: The battery must be removed to access the ABS module electrical connector.
   • Remove the battery. Refer to the appropriate procedure in Battery, Mounting and Cables article
   • Verify all ABS module-to-HCU fasteners are tightened to their correct torque specifications.
   • Are the ABS module-to-HCU fasteners tightened correctly? 

     Yes	No
     Go to  AC9.	TIGHTEN all ABS module-TO-HCU fasteners to their specified torque value. Go to  AC8.

8. AC8: CHECK FOR RETURNING ABS MODULE DTCS 
   • Install the battery. Refer to the appropriate procedure in Battery, Mounting and Cables article
   • Ignition ON, engine OFF.
   • Clear the ABS DTCs.
   • Ignition OFF.
   • Ignition ON, engine OFF.
   • Press and release the brake pedal at least 3 times.
   • Carry out the ABS self-test.
   • Is DTC C0040:xx or C0044:xx still present? 

     Yes	No
     Go to  AC9.	The condition causing the concern has been repaired. RETURN the vehicle to the customer.

9. AC9: VERIFY ALL WIRING CONNECTIONS 
   • Ignition OFF.
     NOTE: The battery must be removed to access the ABS module electrical connector.
   • ABS Module connector disconnected. (C135)
10. AC10: CHECK FOR CORRECT ABS MODULE OPERATION 
    • BPP Switch connector connected. (C278) Make sure the connector seats and latches correctly.
11. AC11: CHECK FOR CORRECT HCU OPERATION 
    • BPP Switch connector connected. (C278) Make sure the connector seats and latches correctly.
12. AC12: CHECK FOR CORRECT ABS OPERATION 
    • BPP Switch connector connected. (C278) Make sure the connector seats and latches correctly.