Fuel Fired Booster Heater (FFBH)

WARNING: This page is about a different car, the 2020 Jaguar XE and 2019 Jaguar XE. However, it is still accessible from the selected car via links, so may be relevant.

Operation of the Fuel Fired Booster Heater (FFBH) is controlled by a status message from the HVAC Control Module to the Fuel Fired Booster Heater Control Module (FFBHCM). A similar status message, from the control module to the HVAC, advises the HVAC of the current operating status of the FFBH.

While the engine is running, if the ambient air temperature is less than 12 °C (54 °F) (on vehicles with diesel engine) or 1 °C (34 °F) (on vehicles with petrol engine) and the engine coolant temperature is less than 75 °C (167°F) the HVAC changes the status message from 'heater off' to 'supplemental heat'. The FFBHCM then changes the status message it sends the HVAC to 'supplemental heat' and starts the FFBH.

If the engine is started and the FFBH is requested, the HVAC closes the recirculation door for the first 4 minutes or until the vehicle road speed exceeds 16 km/h (10 mph), after which time the HVAC opens the door to enable the ingress of fresh air. This feature is overridden if the MAX demist switch on the Integrated Control Panel (ICP) is selected or if the HVAC detects a risk of misting of the windshield.

The FFBH will not start, or will discontinue operation, if any of the following occur:

The FFBHCM is in the error lockout mode (see DIAGNOSTICS below).
The engine stops running for approximately 4 seconds. The time delay is included for stall detection.
The HVAC receives a 'fuel cut-off' message from the Body Control Module/Gateway Module (BCM/GWM) assembly on the High Speed (HS) Controller Area Network (CAN) comfort systems bus. The BCM/GWM assembly sends the message if it receives a crash signal from the Restraints Control Module (RCM). For additional information, Refer to: AIRBAG SUPPLEMENTARY RESTRAINT SYSTEM .
The HVAC receives a low fuel level message from the BCM/GWM assembly on the HS CAN comfort systems bus.
The Quiescent Current Control Module (QCCM) disconnects the power supply to the Fuel Fired Booster Heater (FFBH). For additional information, Refer to: BATTERY AND CABLES .

If the FFBHCM does not start the FFBH, or discontinues operation, the status message to the HVAC remains at, or changes to, 'heater off'.

If the ambient air temperature increases to 15 °C (59 °F) on vehicles with diesel engine, or 4 °C (40 °F) on vehicles with petrol engine, or the engine coolant temperature increases to 85 °C (185 °F), the HVAC cancels supplemental heating, by changing the status message to the FFBHCM back to 'heater off'. The FFBHCM then cancels FFBH operation and changes the status message to the HVAC to 'heater off'.