DTC B1D23-15: Overheat Sensor - Circuit short to battery or open: Action

NOTE:

The fuel fired booster heater contains many serviceable components. It should not be necessary to install a new fuel fired booster heater to rectify this fault.
To check the operation of the fuel fired booster heater, perform routine - Auxiliary Heater (AHCM) Activation Test (0x900A). Repeat the routine if excessive smoke is emitted from the fuel fired booster heater exhaust.

Refer to the appropriate SYSTEM WIRING DIAGRAMS information and check the fuel fired booster heater overheat sensor circuit for short circuit to power, open circuit, high resistance. Repair the wiring harness or install a new fuel fired booster heater overheat sensor as necessary