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Circuit/System Testing

WARNING: This page is about a different car, the 2009 GMC Envoy and 2009 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the powertrain relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the powertrain relay controlled output circuit terminal and ground.
    • If the test lamp illuminates, test the powertrain relay controlled output circuit for a short to voltage.
  3. Ignition OFF, verify that a test lamp illuminates between the powertrain relay coil voltage supply circuit terminal and ground.
    • If the test lamp does not illuminate, test the powertrain relay coil voltage supply circuit for a short to ground or an open/high resistance.
  4. Verify that a test lamp illuminates between the powertrain relay switch voltage supply circuit terminal and ground.
    • If the test lamp does not illuminate, test the powertrain relay switch voltage supply circuit for an open/high resistance.
  5. Disconnect the ECM.
  6. Ignition ON, verify that a test lamp illuminates between ECM connector terminal 19 X1 and ground.
    • If the test lamp does not illuminate, test the ignition 1 relay controlled output circuit for a short to ground or open/high resistance. If the circuit tests normal and its fuse is open, replace the ECM.
  7. Ignition OFF, connect the harness connector at the ECM.
  8. Ignition ON, connect a jumper wire between the powertrain relay voltage supply circuit terminal and the powertrain relay controlled output circuit terminal. Verify the EC Ignition Relay Feedback parameter indicates battery positive voltage.
    • If not the specified value, test the powertrain relay controlled output circuit for a short to ground or an open/high resistance. If the circuit tests normal and its fuse is open, replace the ECM.
  9. If all circuits test normal, replace the powertrain relay.
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