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Home >> Chevrolet >> 2020 >> Express 2500 LS, 6.0L Eng VIN G >> Repair and Diagnosis >> External Pages >> Different car >> Section 79 (HVAC - Manual) >> Diagnostic Information and Procedures >> DTC B0440, B0441, or B0442 >> 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.
  1. Ignition OFF, disconnect the harness connector at the glow plug.
  2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal and ground.
    • If greater than the specified range, replace the coolant heater.
  3. Install a test lamp between the control circuit terminal and low reference circuit terminal.
  4. Ignition ON, command the glow plug ON and OFF using a scan tool. Verify the test lamp turns ON and OFF with each command.
    • If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the coolant heater.
    • If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the coolant heater.
  5. If all circuits test normal, test or replace the glow plug.
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