Buick Regal: 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/System Description

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

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:Outside Ambient Air Temperature Sensor Signal & Intake Air Temperature Sensor Signal

P0072

Outside Ambient Air Temperature Sensor Signal=Greater than 88ºC (190ºF)

P0073

Outside Ambient Air Temperature Sensor Signal=Less than -40ºC (-40ºF)

P0074

Outside 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.

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

Reference Information

Schematic Reference

Instrument Cluster Wiring Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEW INDEX

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

Scan Tool Reference

Control Module References

Circuit/System Verification

1. Ignition - On / Vehicle - In Service Mode.

2. Verify the scan tool parameter:Ambient Air Temperature=-40 to 88ºC (-40 to 190ºF) and changes.

• If not between -40 and 88ºC (-40 and 190ºF) or does not change
• Refer to: Circuit/System Testing
• Go to next step: If between -40 and 88ºC (-40 and 190ºF) and changes

3. All OK.

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(or2) & 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(or2)@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 -34ºC (-30ºF).

• If -34ºC (-30ºF) 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(or1)@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 -35ºC (-31ºF) or colder

6. Connect a 3 A fused jumper wire between the test points: Signal circuit terminal A(or1) & Low Reference circuit terminal B(or2).

7. Verify the scan tool parameter:Ambient Air Temperature = Greater than 143ºC (290ºF).

• If 143ºC (290ºF) 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 144ºC (291ºF) or warmer

8. Connect the component: B9 Ambient Air Temperature Sensor.

9. Operate the vehicle within the Conditions for Running the DTC.

10. Verify the DTC does not set.

• If the DTC sets

Replace the component: B9 Ambient Air Temperature Sensor

• Go to next step: If the DTC is not set

11. 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

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