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Home › Hummer › 2008 › H2 4D Utility Pickup › Repair and Diagnosis › Engine Performance › System › Engine Controls And Fuel - 6.2L - DTC P1255 To DTC P2635 › DTC P1258 › Circuit/System Verification

Circuit/System Verification

IMPORTANT: If DTC P1482 is set, diagnose that DTC first.
  1. Observe the engine coolant level. The engine coolant level should be within operating range. Refer to Capacities - Approximate Fluid, and Engine Coolant in the Owner's Manual.
  2. Ensure that the vehicle has the correct engine coolant, with correct concentration, and is not old, contaminated or contains additives. Refer to Recommended Fluids and Lubricants in the Owner's Manual.
  3. Inspect the cooling system for the following:
    • Leaks
    • Kinked or pinched hoses, especially at the radiator
    • Loose, missing, or damaged radiator air seals or deflectors
    • The radiator and A/C condenser for any air flow obstructions or bent fins--Refer to SYMPTOMS - ENGINE COOLING
      IMPORTANT: A small delay occurs before the ECM changes the cooling fan speed.
  4. Command the cooling fan speed from 0% to 100% with a scan tool.

    If the fan speed does not transition with the commanded states, refer to COOLING FAN INOPERATIVE

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