Auto Stop/Start System

WARNING: This page is about a different variant/trim than selected.

The auto stop/start system is controlled by the PCM and the BCM /GWM through the FlexRay. Signals from other system components and modules are used 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 stops the engine in appropriate conditions, resulting in zero exhaust emissions and saving fuel when the vehicle is stationary. When the driver is ready to move off, the engine instantly restarts. Sophisticated controls make sure that the auto 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 or disabled using the auto stop/start soft key on the ICP with touchscreen.

When the dynamic mode selected on the ICP with touchscreen, it will disable the auto stop/start system. The dynamic mode stays on even after the ignition is cycled, it remains selected for 6 hours. If the dynamic mode is switched off, the vehicle system returns to the standard settings.

Auto Stop/Start Operation with the BISG

When the PCM receives an engine restart request, the PCM sends a crank command to the BISG . The crank command to the BISG is sent through the HS CAN power mode zero systems bus. The BISG starts the engine by turning the crankshaft through the BISG drive belt.

The PCM uses the BISG to crank the engine when:

The auto stop/start system is active.
The ambient temperature is above -5°C (23°F).

When there is an error between the BISG and the PCM , the starter motor starts the engine.

Auto Stop/Start Operation Conditions

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 makes sure that all the necessary conditions are satisfied by monitoring, among others:

Brake hydraulic system pressure.
Vehicle speed.
The state of vital vehicle systems.
Environmental conditions.
TCS position.

When all necessary conditions are satisfied, the auto stop/start system automatically stops the engine when:

The vehicle stops from a speed higher than 16 km/h (10 mph).
Sufficient pressure is applied to the brake pedal to make sure that the vehicle is stationary.
The transmission is in DRIVE (D) or SPORT(S).
PARK (P) or NEUTRAL (N) position is selected on the TCS .

The driver is notified that the engine has stopped by the auto stop/start warning indicator being illuminated in the IPC . Other warnings normally associated with an engine stoppage do not illuminate during the engine stop within an auto stop/start cycle. For example, the charge warning indicator and low oil pressure indicators are suppressed.

To restart the engine, the driver must release the brake pedal or press the accelerator pedal. On Mild Hybrid Electric Vehicle (MHEV) depending on the ambient temperature, the PCM then operates the starter motor or the BISG to start the engine.

When system conditions are not approved by the PCM the auto stop/start system does not behave as expected.

For example:

System inhibit - The engine continues running even though the vehicle is stationary with the brake pedal pressed and the 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 activates an early automatic engine restart.

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

Vehicle and occupant safety.
Driver requirements.
Occupant comfort.

The main control logic for auto stop/start operation resides in the PCM . However the BCM /GWM has software to communicate engine stoppage inhibits to the PCM . In some instances the driver is notified of the reason for the intervention. The displayed notifications are depending on the reason for the system intervention.

Stop Inhibitors

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

Driver affected stop inhibitors:

Driver disables the auto stop/start system.
Gear selected on the paddle switch.
The vehicle speed less than 16 km/h (10 mph) after reversing.
The brake pedal is not fully pressed.
The accelerator pedal is pressed.
The hood is open.
The driver door is open.
The vehicle is in dynamic mode.
The driver seatbelt is not fastened.
Climate control system used above calibrated threshold.
Windshield demist is operating.
Trailer electrical connection detected.
Adaptive cruise control is operating.
Steering angle rate changed.

Vehicle system affected stop inhibitors:

Startup battery cold cranking capability below threshold.
Startup battery State Of Charge (SOC) is low.
Catalytic converter outside either pre or post calibration range.
Engine coolant temperature below threshold.
Engine oil temperature below threshold.
BISG error report to PCM (if equipped).
Park brake fault.
Control module fault report to PCM . For example: Power Steering Control Module (PSCM).

Environmental effected start initiators:

Ambient air temperature rises above 40°C (104°F).
Ambient air temperature falls below -5°C (23°F).

The maximum engine stop duration is 270 seconds, the vehicle starts after this time.

Start Inhibitors

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

Driver effected start inhibitors:

The hood has been opened.
The driver seatbelt is disengaged. (This is an automatic start inhibitor, therefore the engine can be restarted by releasing the brake pedal or operating the accelerator pedal.)
The driver door is unlatched. (This is an automatic start inhibitor, therefore the engine can be restarted by releasing the brake pedal or operating the accelerator pedal.)

Vehicle system inhibitor:

There is a system fault.