Vehicles With Auto Stop/Start System: Notes

WARNING: This page is about a different car, the 2018 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 ignition switch is operated, the auto stop/start system operates in the same way as on vehicles without auto stop/start system.

Once engine cranking has been granted, the Powertrain Control Module (PCM) energizes the starter relay located in the Engine Junction Box 2 (EJB 2). The closing of the starter relay contacts causes the power feed to be applied to the motor solenoid, which energizes and transmits current into the motor brushes and armature. The armature rotational force is transferred to the drive plate ring gear through the pinion gear. This rotates the drive plate and starts the engine.

The auto stop/start system automatically stops the engine in appropriate conditions, resulting in zero exhaust 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 provide that the auto stop/start system does not compromise the needs of either the driver or the vehicle.

By default the auto 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 JaguarDrive Switchpack (JDS).

Software within the PCM controls the operation of the auto 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 provides all the necessary conditions are satisfied by monitoring, among others:

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

If all necessary conditions are satisfied the auto 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 make sure that the vehicle is stationary and the transmission is in Drive (D) or Sport (S).
The vehicle is stationary and Park (P) or Neutral (N) selected on the Transmission Control Switch (TCS).

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

To restart the engine, the driver must release the brake pedal or press 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 Transmission Control Switch (TCS) in Drive (D) or Sport (S). Another condition is when the vehicle is stationary and the TCS is in Park (P) or Neutral (N).
System override: The engine has been stopped by the auto stop/start system but conditions have since changed, this will activate an early automatic engine restart.

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

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

The main control logic for auto stop/start operation resides in the Powertrain Control Module (PCM). However the Body Control Module/Gateway Module (BCM/GWM) assembly has software to communicate engine stoppage 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.