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Home >> GMC >> 2018 >> Acadia Denali, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 238 (HVAC System - Automatic) >> Diagnostic Information and Procedures >> DTC B0178 or B0514: Duct Air Temperature Sensor >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2017 Cadillac ATS. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the appropriate temperature sensor. It may take up to 10 min for all vehicle systems to power down.
    2. NOTE:

    The scan tool must be disconnected from the vehicle before performing the next test.

  2. Test for less than 10 Ω between the low reference circuit terminal B and ground.
    • If 10 Ω or greater 
    1. Ignition OFF, disconnect the harness connectors at the K33 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 K33 HVAC Control Module.
    • If less than 10 Ω 
  3. Ignition ON.
  4. Verify the appropriate scan tool temperature sensor parameter is less than -37°C (-35°F)
    • If greater than -37°C (-35°F) 
    1. Ignition OFF, disconnect the harness connectors at the K33 HVAC Control Module.
    2. Test for infinite resistance between the signal circuit terminal A and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the K33 HVAC Control Module.
    • If -37°C (-35°F) or less 
  5. Install a 3 A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B.
  6. Verify the scan tool temperature sensor parameter is greater than 77°C (170°F).
    • If less than 77°C (170°F) 
    1. Ignition OFF, remove the jumper wire and disconnect the harness connectors at the K33 HVAC Control Module, ignition ON.
    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
    3. Ignition OFF
    4. 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 K33 HVAC Control Module.
    • If 77°C (170°F) or greater 
  7. Test or replace the temperature sensor.
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