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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 250 (Automatic Transmission - 6L50/6L80/6L90 - DTC P0218 To DTC P0971) >> DTC P0634 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2008 GMC Yukon XL, 2008 GMC Yukon, 2008 Chevrolet Tahoe, 2008 Chevrolet Suburban, and 2008 Cadillac Escalade EXT. However, it is still accessible from the selected car via links, so may be relevant.
  1. Start the engine.
  2. Observe the transmission fluid temperature (TFT) and the engine coolant temperature (ECT). Ensure there are no current overheat conditions present in these systems.
    • If an overheating concern is found, diagnose and repair that system first.
  3. Operate the vehicle under the same conditions as found in Failure Records and observe the TCM Temperature parameter on the scan tool.
  4. Recheck for DTCs.
    • If the DTC resets, and the TCM power-up temperature sensor is not over 130°C (266°F), and the TFT is less than 120°C (248°F), replace the control solenoid (w/body and TCM) valve assembly.
    • If the TCM power-up temperature sensor is over 130°C (266°F), inspect and repair the transmission cooler, transmission cooler fluid lines, engine cooling system, and transmission fluid level, and inspect for any obstructions in the cooling system airflow which may cause an overheat condition.
  5. Inquire about customer towing or extreme driving conditions.
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