Code Definition

B2459 — Aux Heater Overheat Sensor Circuit Open

System: Body  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About B2459

B2459 is a generic (obd-ii standard) body diagnostic trouble code. It belongs to the B-prefix family of codes, which covers body, interior, airbag, or comfort-electronics faults.

When B2459 is stored, the module has detected an open (broken or disconnected) electrical path in the monitored circuit; and a sensor-related fault — the reported value from the named sensor is out of spec.

Scanning & clearing: Body (B) codes are often stored in the body control module, airbag module, or climate module. A basic OBD-II tool usually will not read body codes — an enhanced or OEM-level scan tool is typically required.

Because B2459 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The auxiliary heater overheat sensor is a dedicated temperature sensor mounted directly on the heat exchanger or burn chamber of the auxiliary heater, separate from the main coolant temperature sensor, that watches for thermal runaway conditions and shuts down the heater before damage occurs. It is typically a thermistor or thermal switch monitored by a pull up reference voltage in the auxiliary heater control module, with the signal voltage falling as housing temperature rises. DTC B2459 is set when the controller detects the overheat sensor signal floating at the reference voltage with no cu...

Join TaT to view the complete code information and diagnostic details.

Quick Facts