Description And Operation: Operation: Diagnostics

WARNING: This page is about a different car, the 2018 Jaguar XE and 2017 Jaguar XE. However, it is still accessible from the selected car via links, so may be relevant.

The FFBHCM monitors the Fuel Fired Booster Heater (FFBH) system for faults. Any faults detected are stored in a volatile memory in the FFBHCM, which can be interrogated by Jaguar approved diagnostic equipment via the High Speed (HS) Controller Area Network (CAN) comfort systems bus. A maximum of three faults and associated freeze frame data can be stored at any one time. If a further fault is detected, the oldest fault is overwritten by the new fault.

The FFBHCM also incorporates an error lockout mode of operation that inhibits operation to prevent serious faults from causing further damage to the system. In the error lockout mode, the FFBHCM immediately stops the FFBH fuel pump, and stops the combustion air fan and coolant pump after the cool down time. Error lockout occurs for start sequence failures, combustion flameouts, heat exchanger casing overheat and if battery voltage is out of limits.

Start failure and flameout: If a start sequence fails to establish combustion, or a flame-out occurs after combustion is established, the FFBHCM immediately initiates another start sequence. The start failure or flameout is also recorded by an event timer in the FFBHCM. The event timer is increased by one after each start failure or flameout, and decreased by one if a subsequent start is successful. If the event timer increases to three (over any number of drive cycles), the FFBHCM enters the error lockout mode.
Heat exchanger casing overheat: To protect the system from excessive temperatures, the FFBHCM enters the error lockout mode if the heat exchanger coolant temperature exceeds 125 °C (257 °F).
Battery voltage out of limits: Error lockout will occur if battery voltage is outside the limits of 10.5 Volts to 16.0 Volts.
The error lockout mode can be cleared using Jaguar approved diagnostic equipment, or by disconnecting the battery power supply to the FFBH for a minimum of 10 seconds.