DTC B12B9-87: Auxiliary Heater Control Module - Missing message: Action

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NOTE: The fuel fired booster heater assembly contains many serviceable components. It should NOT be necessary to replace the entire fuel fired booster heater unit to rectify this fault

Refer to the appropriate system wiring diagrams and check the fuel fired booster heater power and ground circuits for open circuit, high resistance
Refer to the appropriate system wiring diagrams and check the LIN circuit for short circuit to ground, short circuit to power, open circuit, high resistance
Using JLR approved diagnostic equipment, clear the DTCs and perform routine - Auxiliary Heater (AHCM) Activation Test (0x900A). This will operate the fuel fired booster heater for 15 minutes. Note that the routine should be started only when the engine is cool. The routine should be performed with the engine running and with the climate controls set to maximum heat and maximum fan. Repeat the routine again if smoke continues to be visible from the fuel fired booster heater exhaust pipe or from the area surrounding the fuel fired booster heater
If the fault persists, install a new fuel fired booster heater control module located within the fuel fired booster heater, clear the DTCs and perform routine - Auxiliary Heater (AHCM) Activation Test (0x900A)