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Home >> Buick >> 2020 >> Envision Premium >> Repair and Diagnosis >> Brakes >> Mechanical - Hydraulic >> Hydraulic Brakes >> Diagnostic Information and Procedures >> DTC C025E >> Circuit/System Testing

Circuit/System Testing

  1. Ignition ON.
  2. Verify that DTCs P0556, P0557, or P0558 are not set.
    • Go to next step: If none of the DTCs are set 
  3. Ignition OFF/Ignition OFF/Vehicle OFF and all vehicle systems OFF, disconnect the harness connector at the B19B Brake Booster Vacuum Sensor. It may take up to 2 min for all vehicle systems to power down.
  4. Test for less than 10 Ω between the low reference circuit terminal 2 and ground.
    • If 10 Ω or greater 
    1. Disconnect the harness connector at the K20 Engine Control Module.
    2. Test for less than 2 Ω in the low reference circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K20 Engine Control Module.
    • Go to next step: If less than 10 Ω 
  5. Ignition ON/Ignition ON/Vehicle in Service Mode.
  6. Test for 4.8 - 5.2 V between the 5 V reference circuit terminal 3 and ground.
    • If less than 4.8 V 
    1. Ignition OFF/Ignition OFF/Vehicle OFF, disconnect the harness connector at the K20 Engine Control Module.
    2. Test for infinite resistance between the 5 V reference circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • Go to next step: If infinite resistance
    3. Test for less than 2 Ω in the 5 V reference circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K20 Engine Control Module.
    • If greater than 5.2 V 
    1. Ignition OFF/Ignition OFF/Vehicle OFF, disconnect the harness connector at the K20 Engine Control Module, ignition ON.
    2. Test for less than 1 V between the 5 V reference circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K20 Engine Control Module.
    • Go to next step: If between 4.8 - 5.2 V 
  7. Test for less than 1 V between the B19B Brake Booster Vacuum Sensor signal circuit terminal 1 and ground.
    • If greater than 1 V 
    1. Ignition OFF/Ignition OFF/Vehicle OFF, disconnect the harness connector at the K20 Engine Control Module, ignition ON.
    2. Test for less than 1 V between the signal circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K20 Engine Control Module.
    • Go to next step: If less than 1 V 
  8. Ignition OFF/Ignition OFF/Vehicle OFF, disconnect the harness connector at the K20 Engine Control Module.
  9. Test for infinite resistance between the B19B Brake Booster Vacuum Sensor signal circuit terminal 1 and ground.
    • If less than infinite resistance 

      Repair the short to ground on the circuit.

    • Go to next step: If infinite resistance 
  10. Test for less than 2 Ω in the B19B Brake Booster Vacuum Sensor signal circuit end to end.
    • If 2 Ω or greater 

      Repair the open/high resistance in the circuit.

    • Go to next step: If less than 2 Ω 
  11. Replace the B19B Brake Booster Vacuum Sensor.
  12. Verify the DTC does not set while operating the vehicle under the Conditions for Running the DTC.
    • If the DTC does not set 

      All OK

    • Go to next step: If the DTC sets 
  13. Replace the K20 Engine Control Module
  14. Verify the DTC does not set while operating the vehicle under the Conditions for Running the DTC.
    • If the DTC does not set 

      All OK

    • Go to next step: If the DTC sets 
  15. Replace the K17 Electronic Brake Control Module
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