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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 145 (Engine Control System & Fuel - 4.8L, 5.3L, 6.0L And 6.2L - DTC P0335 To DTC P3449) >> DTC P0685, P0689, or P0690 >> Circuit/System Testing

Circuit/System Testing

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  1. Ignition OFF, disconnect the powertrain relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the relay coil control circuit and ground.
    • If the test lamp illuminates, test the relay coil control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  3. Verify that a test lamp does not illuminate between the relay ignition 1 voltage circuit and ground.
    • If the test lamp illuminates, test the relay ignition 1 voltage circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  4. Verify that a test lamp illuminates between the relay coil B+ and ground.
    • If the test lamp does not illuminate, test the relay coil B+ circuit for a short to ground or an open/high resistance.
  5. Verify that a test lamp illuminates between the relay switch B+ and ground.
    • If the test lamp does not illuminate, test the relay switch B+ circuit for a short to ground or an open/high resistance. If the circuits test normal and the fuse for the ignition 1 voltage circuit is open, test the ignition 1 voltage circuit to the ECM for a short to ground. If the circuit tests normal, replace the ECM.
  6. Connect a test lamp between the relay coil B+ and the relay coil control circuit.
  7. Ignition ON, command the powertrain relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the relay coil control circuit for a short to ground. If the circuit tests normal, replace the ECM.
    • If the test lamp is always OFF, test the relay coil control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
  8. Connect a 20A fused jumper wire between the relay switch B+ and the relay ignition 1 voltage circuit.
  9. Ignition ON, engine OFF, monitor the EC Ignition Relay Feedback parameter with a scan tool. The parameter should display B+.
    • If the parameter does not display B+, test the ignition 1 voltage circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  10. If all circuits test normal, test or replace the relay.
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