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Tahoe / Yukon Service Manual

DTC P0071-P0074

Diagnostic Instructions Perform the Diagnostic System Check prior to using this diagnostic procedure: Diagnostic System Check - Vehicle Review the description of Strategy Based Diagnosis: Strategy Based Diagnosis An overview of each diagnostic category can be found here: Diagnostic Procedure Instructions DTC Descriptors DTC P0071 Ambient Air Temperature Sensor Performance DTC P0072 Ambient Air Temperature Sensor Circuit Low Voltage DTC P0073 Ambient Air Temperature Sensor Circuit High Voltage DTC P0074 Ambient Air Temperature Sensor Circuit Intermittent Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performanc
Signal P0072 P0073 P0073 P0071/P0074
Low Reference — P0073 — P0071

Circuit/System Description For an overview of the component/system, refer to: Instrument Cluster Description and Operation

Circuit Description
Signal The control module input circuit has an internal resistance connected to 5 V.
Low Reference Grounded through the control module.
Component Description
B9 Ambient Air Temperature Sensor The temperature sensor is a negative temperature coefficient thermistor, a resistor which changes based on temperature.
K20 Engine Control Module The K20 control module monitors the B9 ambient air temperature sensor. The control module converts the analog voltage signal input to a temperature value.

Conditions for Running the DTC Ignition » On / Vehicle » In Service Mode Conditions for Setting the DTC P0071 The difference between the following parameters is greater than a predefined value: Ambient Air Temperature Sensor Signal & Intake Air Temperature Sensor Signal P0072 Ambient Air Temperature Sensor Signal = Greater than 88°C (190°F) P0073 Ambient Air Temperature Sensor Signal = Less than -40°C (-40°F) P0074 Ambient Air Temperature Sensor Signal = Not Plausible Action Taken When the DTC Sets DTCs listed in the DTC Descriptor category = Type B DTC Air Conditioning Compressor Clutch = Disabled The control module uses default replacement values. Conditions for Clearing the DTC The conditions for setting the DTC no longer exist. Diagnostic Aids The displayed temperature is a filtered value that updates periodically while driving. The value rarely changes when the vehicle is parked. Performing the ECM scan tool Ambient Air Temperature Calculation Reset function (when available) can aid in updating the displayed temperature more quickly. For an overview of the component/system, refer to: Instrument Cluster Description and Operation Reference Information Schematic Reference Instrument Cluster Schematics Connector End View Reference Master Electrical Component List Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs DTC Type Reference Powertrain Diagnostic Trouble Code (DTC) Type Definitions Control Module References Circuit/System Verification

  1. Ignition ON/Vehicle in Service Mode.
  2. Verify DTC P0072, P0073, or P0074 is not set. ⇒ If DTC P0072, P0073, or P0074 is set Refer to Circuit/System Testing. ⇓ If DTC P0072, P0073, or P0074 are not set
  3. Verify any other ECM or temperature-related DTCs are not set. ⇒ If other DTCs are set Refer to Diagnostic Trouble Code (DTC) List - Vehicle. ⇓ If no other DTCs are set
  4. Allow vehicle to completely cool to ambient temperature.
  5. Verify the scan tool Intake Air Temperature Sensor parameter is within 15°C (27°F) of actual ambient temperature. ⇒ If not within 15°C (27°F) of actual ambient temperature Refer to appropriate Intake Air Temperature Sensor diagnosis. ⇓ If within 15°C (27°F) of actual ambient temperature
  6. Verify the scan tool ECM Ambient Air Temperature parameter is within 15°C (27°F) of actual ambient temperature. ⇒ If not within 15°C (27°F) of actual ambient temperature Refer to Circuit/System Testing. ⇓ If within 15°C (27°F) of actual ambient temperature
  7. All OK. Circuit/System Testing
  1. Ignition/Vehicle & All vehicle systems » Off
  2. Disconnect the electrical connector: B9 Ambient Air Temperature Sensor
  3. Test for less than 10 Ω between the test points: Low Reference circuit terminal B ( or 2) & Ground ⇒ If 10 Ω or greater 3.1. Disconnect the electrical connector: K20 Engine Control Module 3.2. Test for less than 2 Ω between the test points: Low Reference circuit terminal B ( or 2) @ Component harness & The other end of the circuit ⇒ If 2 Ω or greater » Repair the open/high resistance in the circuit. ⇒ If less than 2 Ω » Replace the component: K20 Engine Control Module ⇓ If less than 10 Ω
  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 5.1. Ignition/Vehicle » Off 5.2. Disconnect the electrical connector: K20 Engine Control Module 5.3. 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 ⇓ 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 7.1. Ignition/Vehicle » Off & Remove » Jumper wire(s) 7.2. Disconnect the electrical connector: K20 Engine Control Module 7.3. Ignition » On / Vehicle » In Service Mode 7.4. 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. ⇓ If less than 1 V 7.5. Ignition/Vehicle » Off 7.6. Test for less than 2 Ω between the test points: Signal circuit @ Component harness & The other end of the circuit ⇒ If 2 Ω or greater » Repair the open/high resistance in the circuit. ⇒ If less than 2 Ω » Replace the component: K20 Engine Control Module ⇓ If 144°C (291°F) or warmer
  8. Apply dielectric grease to connector terminals.
  9. Connect the component: B9 Ambient Air Temperature Sensor
  10. Operate the vehicle within the Conditions for Running the DTC.
  11. Verify the repair corrected the DTC/symptom. ⇒ If the repair did not correct the DTC/symptom Test or replace the component: B9 Ambient Air Temperature Sensor ⇓ If the repair corrected the DTC/symptom
  12. All OK. Component Testing Static Test
  13. Place the B9 Ambient Air Temperature Sensor in a stable, temperature-controlled area for at least 10 minutes, then measure the resistance between sensor signal terminal A (or 1) and the low reference circuit terminal B (or 2).
  14. Compare the readings with the Ambient Air Temperature Sensor Resistance ⇒ If not in the specified range Replace the component: B9 Ambient Air Temperature Sensor ⇓ If in the specified range
  15. All OK. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification Displays and Gauges Component Replacement Reference For control module replacement, programming, and setup refer to: Control Module References