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Home › Hummer › 2009 › H3T Base, Automatic › Repair and Diagnosis › Transmission › Automatic Trans › Automatic Transmission - DTC P0218 To DTC P2771 › DTC P0976 or P0977 › Circuit/System Testing

Circuit/System Testing

    IMPORTANT: Additional DTCs may set when disconnecting the automatic transmission inline 20-way connector.
  1. Ignition OFF, disconnect the AT inline 20-way connector at the transmission.
  2. Install the J 45681  jumper harness, on the engine side of the AT inline 20-way connector.
  3. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal L and ground.
    • If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test all components connected to the ignition circuit and replace as necessary.
  4. Connect a test lamp between the control circuit terminal B and the ignition circuit terminal L.
  5. Command the 2-3 SS 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 control circuit for a short to ground. If the circuit tests normal, replace the TCM.
    • If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the TCM.
  6. If all circuits test normal, test the automatic transmission internal wiring harness and the 2-3 shift solenoid.
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