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Home >> Chevrolet >> 2020 >> Express 2500 LS, 6.0L Eng VIN G >> Repair and Diagnosis >> External Pages >> Different car >> Section 29 (Hydraulic Brakes) >> Diagnostic Information and Procedures >> Brake Warning Indicator Malfunction (with UJ1) >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2019 GMC Savana 3500, 2019 GMC Savana 2500, 2019 Chevrolet Express 3500, and 2019 Chevrolet Express 2500. However, it is still accessible from the selected car via links, so may be relevant.

Park Brake Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the park brake switch.
  2. Ignition ON, verify the scan tool BCM Park Brake Switch parameter is Released.
    • If not the specified value, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the BCM.
  3. Install a 3A fused jumper wire between the signal circuit terminal A and ground. Verify the scan tool BCM Park Brake Switch parameter is Applied.
    • If not the specified value, test the signal circuit for a short to voltage or an open/high resistance.
  4. If all circuits test normal, test or replace the park brake switch.

Brake Fluid Level Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the brake fluid level switch.
  2. Test for less than 10 ohm between the ground circuit terminal A and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool IPC Brake Fluid parameter is Ok.
    • If not the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the IPC.
  4. Install a 3A fused jumper wire between the signal circuit terminal B and ground. Verify the scan tool IPC Brake Fluid parameter is Low.
    • If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the IPC.
  5. If all circuits test normal, test or replace the brake fluid level switch.

Brake Booster Fluid Pressure/Flow Alarm Switch Malfunction

  1. Ignition OFF, disconnect the X2 harness connector at the brake booster fluid flow alarm switch.
  2. Test for less than 10 ohm between the ground circuit terminal B and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition OFF, disconnect the harness connector at the brake booster fluid pressure alarm switch.
  4. Ignition ON, test for B+ between the signal circuit terminal A and ground.
    • If less than the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the IPC.
  5. Ignition OFF, reconnect the harness connector at the brake booster fluid pressure alarm switch and disconnect the X1 harness connector at the brake booster fluid flow alarm switch.
  6. Ignition ON, test for B+ between the signal circuit terminal A and ground.
    • If less than the specified value, test the signal circuit between the sensors for a short to ground or an open/high resistance. If the circuit tests normal, replace the brake booster fluid pressure alarm switch.
  7. If all circuits test normal, replace the brake booster fluid flow alarm switch.
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