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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 453 (HVAC System - Manual) >> Diagnostic Information and Procedures >> DTC B0158 >> Circuit/System Testing

Circuit/System Testing

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IMPORTANT:

If the ambient air temperature sensor is in temperatures below 2°C (35°F) the compressor clutch will be disabled until the vehicle is driven above 45 mph (72 km/h), the ignition is OFF for more than 3 hours or an instant OAT update is performed.

IMPORTANT:

An instant OAT update must be performed by pressing the A/C and Recirc buttons at the same time before and after the system has been serviced to update the filtered ambient air temperature sensor circuit and convert the A/C permission from withheld to granted.

  1. Ignition OFF, all vehicle systems OFF, and the scan tool disconnected, disconnect the harness connector at the ambient air temp sensor. It may take up to 2 minutes for all vehicle systems to power down.
  2. Test for less than 5 Ω between the low reference circuit terminal B and ground:
    • If 5 Ω or greater 
    1. Ignition OFF, disconnect the X2 harness connector at the HVAC control module.
    2. Test for less than 2 Ω in the low reference circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the HVAC control module.
    • If less than 5 Ω 
  3. Ignition ON.
  4. Test for 4.8-5.2 V between the signal circuit terminal A and ground:
    • If less than 4.8 V 
    1. Ignition OFF, disconnect the X2 harness connector at the HVAC control module.
    2. Test for infinite resistance between the signal circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the signal circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the HVAC control module.
    • If greater than 5.2 V 
    1. Ignition OFF, disconnect the X2 harness connector at the HVAC control module.
    2. Test for less than 1 V between the signal circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the HVAC control module.
    • If between 4.8-5.2 V 
    5. IMPORTANT:

    An instant OAT update must be performed to grant A/C permission after testing or replacing the ambient air temperature sensor.

  5. Replace the ambient air temperature sensor.
  6. Verify the DTC does not set while operating the vehicle under the Conditions for Running the DTC.
    • If the DTC sets 

      Replace the HVAC control module.

    • If the DTC does not set 
  7. All OK.
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