Vehicles With Auto Stop/Start System

WARNING: This page is about a different car, the 2018 Land Rover Discovery Sport. 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 Battery Junction Box (BJB). Closing of the starter relay contacts causes the power feed to be applied to the starter motor solenoid. The starter motor solenoid 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. This result in zero exhaust emissions and saving fuel that would otherwise be used at idle speed 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 Terrain Response (TR) switchpack.

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 system warning indicator being illuminated in the Instrument Cluster (IC). Other warnings normally associated with 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.

For example:

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 PCM. However the Central Junction Box (CJB) 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 Instrument Cluster (IC) message center, of the reason for the intervention.

Stop Inhibitors

The following conditions will prevent the auto stop/start system from stopping the engine.

Driver effected stop inhibitors:

Driver disables the auto stop/start system.
Brake pedal not fully pressed.
Accelerator pedal pressed.
Hood is open.
Driver door is open.
Driver seatbelt is not fastened.
Climate control system used above calibrated threshold.
Windshield demist is operating.
Trailer electrical connection detected.

Vehicle system effected stop inhibitors:

Brake booster vacuum below threshold.
Battery cold cranking capability below threshold.
Primary battery state of charge is low.
Catalytic converter outside either pre or post calibration range.
Engine coolant temperature below threshold.
Engine oil temperature below threshold.

Environmental effected stop inhibitors:

Ambient air temperature above 40°C (104°F).
Ambient air temperature below 0°C (32°F).

Start Initiators

When the engine stops within an auto stop/start cycle the following conditions will initiate an early restart within the same auto stop/start cycle.

Driver effected start initiators:

Driver disables the auto stop/start system.
The accelerator pedal is pressed.
Reverse (R) gear is selected on the Transmission Control Switch (TCS).
Vehicle speed above calibrated threshold 3 km/h (2 mph). A restart will only occur if the transmission is in Neutral (N) and the driver is present. For example, the driver seatbelt remains fastened and the driver door remains latched.
Brake booster vacuum below threshold (driver operates brake pedal).
A higher climate control blower speed is selected.
Windshield demist is activated.

NOTE: When the brake pedal is released during an auto restart the Anti-lock Brake System (ABS) control module briefly applies the brakes to hold the vehicle stationary until the engine has restarted.

Vehicle system effected start initiators:

Primary battery cranking capability is near its lower threshold.
Primary battery state of charge is near its lower threshold.
Windshield demist activates.
The passenger compartment temperature decreases below or increases above the selected thresholds.

Environmental effected start initiators:

Ambient air temperature rises above 40°C (104°F).
Ambient air temperature falls below 0°C (32°F).

The maximum engine stop duration is 270 seconds, the vehicle will restart after this duration.

Start Inhibitors

When the engine stops within a stop/start cycle certain conditions will prevent an automatic restart.

Driver effected start inhibitors:

Hood has been opened.
Driver seatbelt is disengaged (this is an automatic start inhibitor therefore the engine can be restarted by releasing the brake pedal or pressing the accelerator pedal).
Driver door is unlatched (this is an automatic start inhibitor therefore the engine can be restarted by releasing the brake pedal or pressing the accelerator pedal).

Vehicle system inhibitor:

There is a system fault.