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Ambient Air Temperature Sensor Circuit Malfunction

WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the harness connector at the appropriate temperature sensor.
  2. Ignition OFF, test for less than 10 ohms of resistance between the appropriate low reference circuit terminal and ground.
    • Ambient air temperature sensor terminal B.
    • Evaporator temperature sensor terminal 2.
    • If greater than the specified range, test the low reference circuit for high resistance. If the circuit tests normal, replace the HVAC control module.
  3. Ignition ON, test for 4.8-5.2 volts between the low reference circuit terminal B and the appropriate signal circuit terminal.
    • Ambient air temperature sensor terminal A.
    • Evaporator temperature sensor terminal 1.
    • If less than the specified range, test the signal circuit for high resistance. If the circuit tests normal, replace the HVAC control module.
  4. If all circuits test normal, test or replace the appropriate temperature sensor.
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