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Circuit/System Testing

WARNING: This page is about a different car, the 2010 Pontiac G5 and 2010 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the CHMSL relay.
  2. Ignition OFF, exterior lamps OFF, test for less than 5 Ω between the ground circuit terminal 86 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the control circuit terminal 85 and ground.
  4. Ignition ON, turn the CHMSL relay control ON and OFF by applying and releasing the brake pedal. The test lamp should turn ON and OFF as the brake pedal is applied and released.
    • If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
    • 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 BCM.
  5. If all circuits test normal, replace the CHMSL relay.
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