B1251 – OBD-II DTC

OBD-II DTC B1251 – Air Temperature Internal Sensor Circuit Open

DTC B1251 meaning

DTC B1251 refers to a diagnostic trouble code indicating an issue with the air temperature internal sensor circuit. Specifically, it signifies that there is an open circuit in the sensor, which means that the electrical path is incomplete, preventing the sensor from sending accurate temperature readings to the vehicle’s control module.

DTC B1251 symptoms

Common symptoms associated with DTC B1251 may include:

• Inaccurate air temperature readings
• Malfunction indicator light (MIL) illuminated
• Reduced engine performance
• Increased fuel consumption
• Potential issues with HVAC system performance

DTC B1251 causes

Several factors can lead to the occurrence of DTC B1251, including:

• Faulty air temperature sensor
• Damaged wiring or connectors in the sensor circuit
• Corrosion or poor connections at the sensor or control module
• Short circuits or open circuits in the wiring harness
• Faulty engine control module (ECM) or body control module (BCM)

DTC B1251 seriousness

The seriousness of DTC B1251 can vary depending on the vehicle’s make and model. However, it is generally considered a moderate issue. If left unaddressed, it can lead to:

• Decreased engine efficiency
• Increased emissions
• Potential damage to other engine components

How to diagnose DTC B1251

To diagnose DTC B1251, follow these steps:

1. Use an OBD-II scanner to confirm the presence of DTC B1251.
2. Inspect the air temperature sensor and its wiring for visible damage or disconnections.
3. Check the resistance of the air temperature sensor to ensure it is within specifications.
4. Test the voltage supply to the sensor with a multimeter.
5. Examine the connectors for corrosion or poor contact.
6. Clear the DTC and perform a road test to see if the code reappears.

How to fix DTC B1251 step-by-step instructions

To fix DTC B1251, 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 connections are clean and secure to prevent corrosion.
4. Test the sensor circuit again to confirm proper operation.
5. Clear the DTC using an OBD-II scanner.
6. Perform a road test to ensure the issue is resolved and the code does not return.

How to erase DTC B1251

To erase DTC B1251, 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 engine to verify that the code does not reappear.

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