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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1941 (Hydraulic Brake System) >> Diagnostic Information and Procedures >> DTC P0556, P0557, or P0558 >> Circuit/System Testing

Circuit/System Testing

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. Ignition OFF, disconnect the harness connector at the brake booster vacuum sensor.
  2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal 2 and ground.
    • If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 1 and ground.
    • If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
    • If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  4. Verify the scan tool ECM Brake Booster Pressure Sensor parameter is less than 0.15 volt.
    • If greater than the specified range, test the signal circuit terminal for a short to voltage. If the circuit tests normal, replace the ECM.
  5. Install a 3A fused jumper wire between the signal circuit terminal 3 and the 5-volt reference circuit terminal 1. Verify the scan tool ECM Brake Booster Pressure Sensor parameter is greater than 4.75 volts.
    • If less than the specified range, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
  6. If all circuits test normal, test or replace the brake booster pressure sensor.
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