B1256 – Air Temperature External Sensor Circuit Short To Battery

The ODBII 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.

The severity of ODBII code B1256 is moderate.

Common Causes For: B1255 Air Temperature External Sensor Circuit Open

• 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 misdiagnosis for B1256 Air Temperature External Sensor Circuit Short To Battery

• 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

Common Troubleshooting Steps

When dealing with an OBD-II code B1256, which indicates a problem with the Air Temperature External Sensor Circuit Short to Battery, you can follow these common troubleshooting steps:

• 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.
• Visual Inspection:
• Inspect the wiring and connectors associated with the air temperature sensor. Look for signs of damage, corrosion, or loose connections.
• Check for any frayed wires or exposed conductors that could be causing a short circuit.
• Test the Sensor:
• Locate the air temperature sensor and disconnect it from the wiring harness.
• 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.
• Check for Short Circuits:
• 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.
• Inspect the wiring harness for any signs of wear or damage that could cause a short.
• Inspect the Ground Circuit:
• Ensure that the ground connection for the air temperature sensor is secure and free of corrosion. A poor ground can cause erratic sensor readings.
• Check the Power Supply:
• 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.
• Look for Related Codes:
• Check for any other related trouble codes that may provide additional context for the issue. Sometimes, multiple codes can point to a common problem.
• Consult the Service Manual:
• Refer to the vehicle’s service manual for specific diagnostic procedures and specifications related to the air temperature sensor and its circuit.
• Replace the Sensor:
• If the sensor is determined to be faulty after testing, replace it with a new one.
• Clear Codes and Test Drive:
• After making repairs or replacements, clear the trouble codes and take the vehicle for a test drive to see if the code returns. 1
• Seek Professional Help:
• 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.