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Home >> Cadillac >> 2018 >> Escalade Base, 4WD >> Repair and Diagnosis >> Accessories & Equipment >> Gauges & Instrument Panels >> Instrument Panel System Displays And Gauges >> Diagnostic Information And Procedures >> DTC P0071, P0072, P0073, P0074: Ambient Air Temperature Sensor >> Circuit/System Testing

Circuit/System Testing

    NOTE:

    It may take up to 2 min for all vehicle systems to power down before an accurate ground or low reference circuit continuity test can be performed.

  1. Ignition/Vehicle & All vehicle systems - Off
  2. Disconnect the electrical connector:B9 Ambient Air Temperature Sensor
  3. Test for less than 10 ohms between the test points: Low Reference circuit terminal B (or 2) & Ground
    • If 10 ohms or greater 
    1. Disconnect the electrical connector: K20 Engine Control Module
    2. Test for less than 2 ohms between the test points:Low Reference circuit terminal B (or 2) @ Component harness & The other end of the circuit
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Replace the component: K20 Engine Control Module
    • Go to next step: If less than 10 ohms 
  4. Ignition - On / Vehicle - In Service Mode
  5. Verify the scan tool parameter:Ambient Air Temperature = Less than -34 °C (-30°F)
    • If -34 °C (-30°F) or warmer 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector: K20 Engine Control Module
    3. Test for infinite resistance between the test points:Signal circuit terminal A (or 1) @ Component harness & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • If infinite resistance - Replace the component: K20 Engine Control Module
    • Go to next step: If -35 °C (-31 °F) or colder 
  6. Connect a 3 A fused jumper wire between the test points:Signal circuit terminal a (or 1) & Low Reference circuit terminal B (or 2)
  7. Verify the scan tool parameter:Ambient Air Temperature = Greater than 143 °C (290 °F)
    • If 143 °C (290 °F) or colder 
    1. Ignition/Vehicle - Off & Remove - Jumper wire(s)
    2. Disconnect the electrical connector:K20 Engine Control Module
    3. Ignition - On / Vehicle - In Service Mode
    4. Test for less than 1 V between the test points: Signal circuit @ Component harness & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • Go to next step: If less than 1 V
    5. Ignition/Vehicle - Off
    6. Test for less than 2 ohms between the test points: Signal circuit @ Component harness & The other end of the circuit
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Replace the component: K20 Engine Control Module
    • Go to next step: If 144 °C (291 °F) or warmer 
  8. Test or replace the component: B9 Ambient Air Temperature Sensor
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