B1254 – OBD-II DTC

OBD-II DTC B1254 – Air Temperature External Sensor Circuit Failure

DTC B1254 meaning

DTC B1254 refers to a fault in the Air Temperature External Sensor Circuit. This diagnostic trouble code indicates that the vehicle’s onboard diagnostic system has detected an issue with the external air temperature sensor, which is responsible for measuring the ambient air temperature. This information is crucial for the engine control module (ECM) to optimize engine performance and fuel efficiency.

DTC B1254 symptoms

Common symptoms associated with DTC B1254 may include:

• Inaccurate temperature readings displayed on the dashboard.
• Engine performance issues, such as rough idling or stalling.
• Increased fuel consumption.
• Activation of the check engine light.
• Potential issues with the vehicle’s heating and air conditioning system.

DTC B1254 causes

Several factors can lead to the occurrence of DTC B1254, including:

• Faulty air temperature sensor.
• Wiring issues, such as frayed or damaged wires.
• Corroded or loose electrical connections.
• Short circuits in the sensor circuit.
• Faulty engine control module (ECM).

DTC B1254 seriousness

The seriousness of DTC B1254 can vary depending on the underlying issue. While it may not cause immediate safety concerns, it can lead to:

• Decreased engine performance.
• Increased emissions.
• Potential long-term damage to the engine if not addressed.

It is advisable to diagnose and repair the issue promptly to maintain optimal vehicle performance.

How to diagnose DTC B1254

To diagnose DTC B1254, follow these steps:

1. Use an OBD-II scanner to confirm the presence of the DTC.
2. Inspect the air temperature sensor and its wiring for visible damage.
3. Check the electrical connections for corrosion or looseness.
4. Test the air temperature sensor with a multimeter to ensure it is functioning correctly.
5. Review the vehicle’s service manual for specific testing procedures related to the sensor.

How to fix DTC B1254 step-by-step instructions

To fix DTC B1254, follow these steps:

1. Identify and replace the faulty air temperature sensor if necessary.
2. Repair or replace any damaged wiring or connectors in the sensor circuit.
3. Ensure all electrical connections are clean and secure.
4. Clear any stored DTCs using an OBD-II scanner.
5. Test drive the vehicle to ensure the issue is resolved and the check engine light does not reappear.

How to erase DTC B1254

To erase DTC B1254, follow these steps:

1. Connect an OBD-II scanner to the vehicle’s diagnostic port.
2. Turn on the ignition without starting the engine.
3. Navigate to the “Erase Codes” or “Clear DTCs” option on the scanner.
4. Confirm the action to clear the trouble codes.
5. Disconnect the scanner and start the vehicle to verify that the check engine light is off.

Recommended tools for OBD-II diagnostics

Explore our expert picks: The Best OBD2 Scanners for 2025

Easy-to-use Multimeter for reliable diagnostics: AstroAI Auto-ranging Multimeter

Some of the links on this page may be affiliate links, which means we may earn a small commission if you make a purchase. This helps us keep our DTC database up to date and provide valuable content for free. We only recommend products that we have tested and believe to be the best in their class.