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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1658 (Antilock Brake System - Hybrid 3.6L (Hp5)) >> Diagnostic Information and Procedures >> DTC C1120 or C1121 >> Circuit/System Verification

Circuit/System Verification

WARNING: This page is about a different car, the 2009 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
  1. Verify the 12 V battery state of charge is above 12 V.
    • If the battery state of charge is low, charge the 12 V battery. Refer to Battery Charging .
  2. Using the scan tool, perform the EBCM relearn.
  3. Start the engine and allow it to idle.
  4. Place the transmission in the PARK position.
    5. NOTE: To ensure the complete brake modulator and high pressure accumulator (HPA) pressure relief procedure is allowed to occur; the brake controller must see one brake pedal apply with the engine running followed by a proper shutdown without applying the brake pedal.
  5. Apply and release the brake pedal.
    6. NOTE: The ignition must transition to the OFF position without pausing at ACCESSORY and without applying the brake pedal. This ensures that the brake modulator and HPA pressure relief occurs. This process will take approximately 1-3 minutes.
  6. Turn the ignition OFF without pausing at ACCESSORY and without applying the brake pedal. Remove the key from the ignition.
  7. Wait 3 minutes until the brake modulator and HPA pressure relief is complete.
    8. NOTE: The ignition must remain in the ON position with the engine OFF during this entire procedure.
  8. Ignition ON, brakes unapplied, verify the following EBCM scan tool parameters are within the specified values:
    • Master Cylinder Pressure Sensor Input - Less than 100 kPa (15 psi)
    • Rear Brake Pressure Sensor - Less than 100 kPa (15 psi)
    • Brake Pressure Sensor Input - Less than 100 kPa (15 psi)
    • Accum. Pressure Sensor - Less than 800 kPa (116 psi)
    • If any of the parameters are not within the specified range, replace the brake pressure modulator valve (BPMV).
  9. Brakes unapplied, verify the following EBCM scan tool parameters are within the specified values:
    • BMC Prim. Piston Pos. Sen. 5 V Reference Position - Between 4.75 V and 5.25 V
    • BMC Primary Piston Position Sensor A - Less than 0.8 V
    • BMC Primary Piston Position Sensor B - Greater than 4.2 V
  10. Perform a hydraulic check, refer to Brake Hydraulic and Assist System Diagnosis (Two-mode Hybrid) .
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