B1256: Air Temperature External Sensor Circuit Short To Battery

Definition

The OBD2 code B1256 indicates a short circuit in the air temperature external sensor circuit, causing it to connect directly to the battery voltage, which can lead to incorrect temperature readings

Common causes

Damaged wiring or connectors
Short circuit in the sensor circuit
Faulty air temperature sensor
Corroded connectors
Poor ground connection
Water intrusion in the sensor or wiring
Incorrect installation or replacement of the sensor

Common misdiagnoses

Faulty air temperature sensor
Wiring issues or shorts in the harness
Malfunctioning engine control module (ECM)
Incorrectly installed or damaged connectors
Issues with the climate control system
Faulty ambient temperature sensor
Problems with the HVAC control module

Troubleshooting steps

1. Check the Code

Use an OBD-II scanner to confirm the presence of the B1256 code. Clear the code and see if it returns after a short drive
2. Visual Inspection
3. Inspect the wiring and connectors associated with the air temperature sensor. Look for signs of damage, corrosion, or loose connections
4. Check for any frayed wires or exposed conductors that could be causing a short circuit
5. Test the Sensor
6. Locate the air temperature sensor and disconnect it from the wiring harness
7. Use a multimeter to measure the resistance of the sensor. Compare the readings to the manufacturer's specifications. If the resistance is outside the specified range, the sensor may be faulty and should be replaced
8. Check for Short Circuits
9. With the sensor disconnected, use a multimeter to check for continuity between the sensor signal wire and the battery positive terminal. If there is continuity, there is a short circuit in the wiring
10. Inspect the wiring harness for any signs of wear or damage that could cause a short
11. Inspect the Ground Circuit
12. Ensure that the ground connection for the air temperature sensor is secure and free of corrosion. A poor ground can cause erratic sensor readings
13. Check the Power Supply
14. Verify that the sensor is receiving the correct voltage. With the ignition on, measure the voltage at the sensor connector. It should match the specifications provided in the service manual
15. Look for Related Codes
16. Check for any other related trouble codes that may provide additional context for the issue. Sometimes, multiple codes can point to a common problem
17. Consult the Service Manual
18. Refer to the vehicle's service manual for specific diagnostic procedures and specifications related to the air temperature sensor and its circuit
19. Replace the Sensor
20. If the sensor is determined to be faulty after testing, replace it with a new one
21. Clear Codes and Test Drive
22. After making repairs or replacements, clear the trouble codes and take the vehicle for a test drive to see if the code returns. 1
23. Seek Professional Help
24. If the issue persists after following these steps, it may be necessary to consult a professional mechanic for further diagnosis. By following these steps, you should be able to identify and resolve the issue related to the B1256 code

Definition

Common causes

Common misdiagnoses

Troubleshooting steps

1. Check the Code

2. Visual Inspection

3. Inspect the wiring and connectors associated with the air temperature sensor. Look for signs of damage, corrosion, or loose connections

4. Check for any frayed wires or exposed conductors that could be causing a short circuit

5. Test the Sensor

6. Locate the air temperature sensor and disconnect it from the wiring harness

7. Use a multimeter to measure the resistance of the sensor. Compare the readings to the manufacturer's specifications. If the resistance is outside the specified range, the sensor may be faulty and should be replaced

8. Check for Short Circuits

9. With the sensor disconnected, use a multimeter to check for continuity between the sensor signal wire and the battery positive terminal. If there is continuity, there is a short circuit in the wiring

10. Inspect the wiring harness for any signs of wear or damage that could cause a short

11. Inspect the Ground Circuit

12. Ensure that the ground connection for the air temperature sensor is secure and free of corrosion. A poor ground can cause erratic sensor readings

13. Check the Power Supply

14. Verify that the sensor is receiving the correct voltage. With the ignition on, measure the voltage at the sensor connector. It should match the specifications provided in the service manual

15. Look for Related Codes

16. Check for any other related trouble codes that may provide additional context for the issue. Sometimes, multiple codes can point to a common problem

17. Consult the Service Manual

18. Refer to the vehicle's service manual for specific diagnostic procedures and specifications related to the air temperature sensor and its circuit

19. Replace the Sensor

20. If the sensor is determined to be faulty after testing, replace it with a new one

21. Clear Codes and Test Drive

22. After making repairs or replacements, clear the trouble codes and take the vehicle for a test drive to see if the code returns. 1

23. Seek Professional Help

24. If the issue persists after following these steps, it may be necessary to consult a professional mechanic for further diagnosis. By following these steps, you should be able to identify and resolve the issue related to the B1256 code