B2459 – OBD-II DTC

OBD-II DTC B2459 – Aux Heater Overheat Sensor Circuit Open

DTC B2459 meaning

DTC B2459 refers to an issue with the Auxiliary Heater Overheat Sensor Circuit, specifically indicating that there is an open circuit condition. This means that the vehicle’s onboard diagnostic system has detected that the signal from the auxiliary heater overheat sensor is not reaching the engine control module (ECM) as expected. The auxiliary heater is responsible for providing additional heat to the cabin, especially in cold weather, and the overheat sensor monitors its temperature to prevent overheating.

DTC B2459 symptoms

Common symptoms associated with DTC B2459 may include:

• Increased cabin heating time
• Inconsistent or insufficient cabin heat
• Warning lights on the dashboard, such as the check engine light
• Possible engine overheating if the auxiliary heater is malfunctioning

DTC B2459 causes

Several factors can lead to the triggering of DTC B2459, including:

• Faulty auxiliary heater overheat sensor
• Wiring issues, such as damaged or corroded wires
• Poor electrical connections in the circuit
• Faulty engine control module (ECM)
• Issues with the auxiliary heater itself

DTC B2459 seriousness

DTC B2459 can be considered serious as it may indicate a potential overheating issue with the auxiliary heater. If left unaddressed, this could lead to further damage to the heating system or even engine components. It is advisable to diagnose and repair the issue promptly to ensure safe and effective operation of the vehicle’s heating system.

How to diagnose DTC B2459

To diagnose DTC B2459, follow these steps:

1. Use an OBD-II scanner to confirm the presence of DTC B2459.
2. Inspect the auxiliary heater overheat sensor and its wiring for any visible damage or corrosion.
3. Check the electrical connections for tightness and cleanliness.
4. Test the resistance of the auxiliary heater overheat sensor using a multimeter.
5. Consult the vehicle’s service manual for specific resistance values and compare them to your readings.
6. Check for any additional DTCs that may provide more context to the issue.

How to fix DTC B2459 step-by-step instructions

To fix DTC B2459, follow these steps:

1. Clear the DTC using an OBD-II scanner.
2. Inspect and repair any damaged wiring or connectors related to the auxiliary heater overheat sensor.
3. If the sensor is faulty, replace it with a new one.
4. Ensure all connections are secure and free of corrosion.
5. Recheck the system by starting the vehicle and monitoring for any new DTCs.
6. Test the auxiliary heater operation to ensure it is functioning correctly.

How to erase DTC B2459

To erase DTC B2459, 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 DTC menu on the scanner.
4. Select the option to clear or erase DTCs.
5. Confirm the action and wait for the scanner to complete the process.
6. Disconnect the scanner and start the vehicle to ensure the DTC does not reappear.

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.