Vehicles With Auto Stop/Start

Engine cranking is requested when the engine stop/start switch is pressed and the driver has depressed the brake pedal. When engine cranking is requested, the ECM checks that a valid key code has been received and the transmission is in P (park) or N (neutral) before granting the crank request.

Once engine cranking has been granted, the ECM energizes the starter relay located in the right BJB. The closing of the starter relay contacts causes battery voltage to be applied to the motor solenoid, which energizes and causes current to flow into the motor brushes and armature. The armature rotational force is transferred to the drive plate ring gear through the pinion gear, rotates the drive plate and starts the engine.

When the engine reaches self-sustaining operating speed, the ECM then de-energizes the starter relay to disconnect power from the starter motor and disengage the pinion gear from the drive plate ring gear.

Auto Stop/Start System 

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 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 floor console. The Light Emitting Diode (LED) in the auto stop/start switch is extinguished when the auto stop/start system is disabled.

Software within the ECM 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 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 Auto stop/start system will automatically stop the engine if:

• The vehicle stops from a speed greater than 2.5 mph (4 km/h).
• Sufficient pressure is applied to the brake pedal to ensure the vehicle is stationary and the transmission is in D or S, or the vehicle is stationary and P or N selected on the Transmission Control Switch (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 Auto stop/start cycle.

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

If system conditions are not approved by the ECM 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 Drive (D) or Sport (S), or 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 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 Auto stop/start operation resides in the ECM, the CJB has software to communicate engine shutdown inhibits to the ECM. In some instances, depending on the reason for the system intervention the driver will be notified, via the IC message center, of the reason for the intervention.

Stop Inhibitors 

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

Driver effected stop inhibitors

• Driver switches off the Auto stop/start system.
• A steering wheel paddle switch has been used to select a gear.
• Brake pedal not fully pressed.
• Accelerator pedal depressed.
• Hood is open.
• Driver door is open.
• Driver seatbelt is not fastened.
• Hill Decent Control (HDC) is active.
• Terrain Response Auto2® mode is active.
• 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.
• 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 has shutdown within a Auto stop/start cycle certain conditions will prevent an automatic restart:

Driver effected start initiators

• Driver switches off the Auto stop/start system.
• The accelerator pedal is pressed.
• A steering wheel paddle switch is operated to select a gear.
• Reverse (R) is selected on the Transmission Control Switch (TCS).
• Vehicle speed above calibrated threshold 2 mph (3 km/h) (a restart will only occur if the transmission is in neutral and the driver is present, for example, the driver seatbelt remains fastened and the driver door remains latched)
• Brake booster vacuum below threshold (driver operating brake pedal).
• A higher climate control blower speed is selected.
• Windshield demist is activated.

Vehicle system effected start initiators

• Battery cranking capability is near its lower threshold.
• 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 has shutdown within a Auto 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 depressing the clutch pedal).
• Driver door is unlatched (this is an automatic start inhibitor therefore the engine can be restarted by depressing the clutch pedal).

Vehicle system inhibitor

• There is a system fault.

Trailer Towing 

The Auto stop/start system will automatically disable when trailer lights are detected by the Central Junction Box (CJB), this information is then transmitted to the Engine Control Module (ECM). It is not possible for the system to detect when a trailer power plug is inserted in the vehicle towing connector, so it uses operation of the trailer lights as its indicator.

The trailer towing system inhibits Auto stop/start operation as it is possible that trailer power requirements could interfere with the operation of the battery monitoring system. In particular, a trailer battery could reverse the supply current to the vehicle during an engine cranking event, this could possibly confuse the battery monitoring system into detecting an unrealistically small current at engine cranking.