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Circuit/System Testing

WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Sun Load Sensor Circuit Malfunction

    IMPORTANT: If a solar load sensor has an out of range condition caused by a short to voltage, short to ground, or an open/high resistance, the scan tool will display the same value: 225 counts.
  1. Ignition OFF, disconnect the harness connector at the sunload sensor.
  2. Test for less than 10 ohms between the ground circuit terminal C and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, test for 4.8-5.2 volts between the ground circuit terminal C and the appropriate signal circuit terminal listed below:
    • Left solar load sensor circuit terminal A.
    • Right solar load sensor circuit terminal B.
    • If less than the specified range, test the signal circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the HVAC control module.
    • If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module.
  4. If all circuits test normal, test or replace the sunload sensor.

Ambient Air Temperature Sensor Circuit Malfunction

  1. Ignition OFF, disconnect the harness connector at the ambient temperature sensor.
  2. Test for less than 1 ohm between the low reference circuit terminal B and ground.
    • If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  3. Ignition ON, verify the scan tool Outside Air Temp. Raw parameter is greater than 4.9 volts or 250 counts.
    • If less than the specified range, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the HVAC control module.
  4. Install a 3-amp fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool Outside Air Temp. Raw parameter is less than 0.1 volt or 5 counts.
    • If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  5. If all circuits test normal, test or replace the ambient temperature sensor.

Inside Air Temperature Sensor Circuit Malfunction

  1. Ignition OFF, disconnect the harness connector at the appropriate inside air temperature sensor.
  2. Test for less than 1 ohm between the ground circuit terminal C and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify a scan tool illuminates between the control circuit terminal B and ground.
    • If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance.
  4. Ignition OFF, test for less than 1 ohm between the low reference circuit terminal B and ground.
    • If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  5. Ignition ON, verify the appropriate scan tool Inside Temp Sensor parameter is greater than 4.9 volts or 250 counts.
    • If less than the specified range, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the HVAC control module.
  6. Install a 3-amp fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool Temp Sensor Voltage parameter is less than 0.1 volt or 5 counts.
    • If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  7. If all circuits test normal, test or replace the appropriate temperature sensor.

Duct Temperature Sensor Circuit Malfunction

  1. Ignition OFF, disconnect the harness connector at the appropriate temperature sensor.
  2. Test for less than 1.0 ohm between the low reference circuit terminal 2 and ground.
    • If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  3. Ignition ON, verify the appropriate Duct Temp Sensor Actual parameter is greater than 4.9 volts or 250 counts.
    • If less than the specified range, test the signal circuit terminal 1 for a short to ground. If the circuit tests normal, replace the HVAC control module.
  4. Install a 3-amp fused jumper wire between the signal circuit terminal 1 and the low reference circuit terminal 2. Verify the scan tool Duct Temp Sensor Actual parameter is less than 0.1 volt or 5 counts.
    • If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  5. If all circuits test normal, test or replace the appropriate temperature sensor.
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