Code Definition

B2457 — Aux Heater Coolant Sensor Circuit Open

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

About B2457

B2457 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 B2457 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 B2457 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 coolant sensor is a negative temperature coefficient (NTC) thermistor that measures the coolant temperature inside or downstream of the auxiliary heater heat exchanger and reports it to the auxiliary heater control module. The controller uses this temperature signal to manage the burn cycle, drive the coolant circulation pump, prevent overheating, and coordinate with the engine ECU and HVAC system. The sensor is supplied with a regulated reference voltage of typically 5V through a fixed pull up resistor in the controller, and its return signal varies as the thermistor resi...

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