Auto Stop/Start System: Notes

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.

At the beginning of a drive cycle, when the stop/start switch is operated, the auto stop/start system operates in the same way as on vehicles without stop/start.

The auto stop/start system is controlled by the Powertrain Control Module (PCM) and the Body Control Module/Gateway Module (BCM/GWM) assembly via High Speed (HS) Controller Area Network (CAN) powertrain systems bus messages and signals from other system components and modules to determine the correct conditions for system operation. The auto stop/start system detects when it is appropriate to stop and start the engine.

The auto stop/start system automatically shuts down the engine in appropriate conditions, resulting in zero tailpipe emissions and saving fuel that would otherwise be used idling the engine when stationary. When the driver is ready to move off, the engine instantly restarts. Sophisticated controls ensure that the stop/start system does not compromise the needs of either the driver or the vehicle.

By default the stop/start system is enabled at the start of each ignition cycle. The auto stop/start system can be enabled/disabled using the auto stop/start switch in the floor console. The Light Emitting Diode (LED) in the auto stop/start switch is extinguished when the stop/start system is disabled.

Software within the PCM controls the operation of the stop/start system. In addition to its own dedicated components the auto stop/start system encompasses many other vehicle systems. Complex technology interconnects these systems and ensures all the necessary conditions are satisfied by monitoring, among others:

Brake hydraulic system pressure.
Transmission Control Switch (TCS) position.
Road speed.
The state of vital vehicle systems.
Environmental conditions.

If all necessary conditions are satisfied the stop/start system will automatically stop the engine if:

The vehicle stops from a speed greater than 4 km/h (2.5 mph).
Sufficient pressure is applied to the brake pedal to ensure the vehicle is stationary and the transmission is in D (Drive) or S (Sport), or the vehicle is stationary and P (Park) or N (Neutral) selected on the TCS.

The driver will be notified that the engine is shutdown by the auto stop/start warning indicator being illuminated in the Instrument Cluster (IC). Other warnings normally associated with an engine shutdown, for example the ignition and low oil pressure indicators, are suppressed so will not illuminate during an engine shutdown in a stop/start cycle.

To restart the engine, the driver simply releases the brake pedal or presses the accelerator pedal. The PCM then operates the starter motor and starts the engine.

If system conditions are not approved by the PCM the auto stop/start system will not behave as expected, examples of this are:

System inhibit: the engine will continue running even though the vehicle is stationary with the brake pedal pressed and the TCS in D (Drive) or S (Sport), or the vehicle is stationary and the TCS is in P (Park) or N (Neutral).
System override: the engine has been stopped by the stop/start system but conditions have since changed, this will activate an early automatic engine restart.

These interventions are to ensure the auto stop/start system does not impact on:

Vehicle and occupant safety:
Driver requirements
Occupant comfort
Vehicle on-road and off-road capabilities.

Although the main control logic for stop/start operation resides in the PCM the Body Control Module/Gateway Module (BCM/GWM) assembly has software to communicate engine shutdown inhibits to the PCM. In some instances, depending on the reason for the system intervention the driver will be notified, via the message center, of the reason for the intervention.