Stop Start

How does Stop/Start function - simple overview:

Stop-Start shuts the engine off when the vehicle stops
The vehicle has to be stopped for a pre-set time before the engine is switched off
Then, it restarts when the driver releases the brake to move the vehicle
The system senses brake pedal position and vehicle speed to determine that the vehicle is moving
Powertrain calibration makes the decision when to shut off the engine and when to restart the engine again
The Stop-Start function is transparent to the driver
When the engine stops, a smaller secondary battery keeps accessory features powered, like the fan, wipers, headlights, audio system, etc.
An in-rush current relay (ICR) is used to smooth out voltage dips when the starter cranks the engine

Primary Autostop Enablers - Brake pedal depressed (automatic transmission).

Secondary Autostop Enablers - Vehicle speed, coolant temperature, hood closed, doors closed, driver's seat belt latched, interior climate and settings, battery state and energy demand, steering wheel angle, steering wheel torque, ambient temperature, time and speed since last autostop, transfer case position, and ESC status, No stop-start related faults present.

Autostop Events

Autostop state broadcast on CAN Bus.
Cluster telltale illuminates.
Engine shutdown begins.

As the engine slows it passes through three phases:

Fuel and spark restart permissible.
Restart prohibited.
Restart permitted, based on start system employed.

Autostart requests are evaluated throughout the autostop event.

When in autostop:

Instrument cluster stop/start telltale remains illuminated.
EVIC displays the autostop state message.
Body controller starter relay is energized providing the engine controller with direct starter control.

Vehicle Function:

Consumer electronics continue to function in a normal manner.
HVAC fan speed and other setting adjusted to maximize cabin comfort and autostop duration (based on climate control settings and conditions).
Electric Power Steering (EPS) maintained during autostop, possibly with reduced maximum assist.

System Requested Autostarts:

Battery State.
Brake Vacuum.
Climate control stress.
Vehicle speed.
Steering wheel angle or torque.
Transmission selector position.

Stop-Start Disable (while autostopped)

Vehicle systems monitored that may disable stop-start (requiring a key restart if in autostop) include: hood opened, occupant sensing indicating driver not present, unsafe gear shift position for autostart and critical system faults.

Autostart Decision:

All autostart enablers present.
Brake pedal released or shifter place in reverse (automatic transmissions).
Clutch pedal depressed past the up-stop position (manual transmission).
Throttle pedal depressed.

Autostart Events:

Autostart state broadcasted on the CAN bus.
instrument cluster stop/start telltale illumination cancelled.
EVIC display changed to previous EVIC message (outside temp and compass, etc).
VSMs are placed in voltage conditioning mode.
Hill Assist requested.
Starter relay commanded to initiate cranking.
Engine achieves idle speed.

Launch Events:

Automatic transmission clutches engaged.
Hill assist released.
Climate control returned to pre-autostop conditions.
Stop-Start Ready state broadcast on the CAN bus.
Embedded EVIC stop-start message indicating "Stop/Start Ready".

Planned Autostart (Engine On) Enable Conditions:
1. Valid target gear and brake switch pressure condition.
2. Completed initial engine key start.
3. Occupant sensing allow engine start condition met.
4. OBD allow engine start condition met.
5. Vehicle hood not Ajar.

Potential Autostop (Engine Off) Enable Conditions:
1. Tow Haul mode not active.
2. Steering wheel angle within defined range.
3. Steering wheel angle gradient within defined range.
4. Steering column torque within defined range.
5. Battery health state of function greater than threshold.

Planned Autostop (Engine Off) Enable Conditions:
1. Valid target gear and brake switch pressure state combination.
2. Threshold vehicle speed exceeded or timed-out since last shift out of reverse.
3. Transmission ready.
4. 4WD Low mode not active.
5. Starter cool down condition met after reaching max allowable consecutive restarts.
6. Ambient temperature within defined range.
7. Engine coolant temperature within defined range.
8. Catalyst temperature within defined range.
9. Battery temperature within defined range.
10. Barometric pressure greater than threshold.
11. Brake booster delta pressure less than threshold.
12. Fuel level greater than threshold.
13. Vehicle hood not Ajar.
14. No throttle request.
15. No engine stop inhibit request by HVAC.
16. Battery state of charge greater than threshold.
17. Battery voltage state of function greater than threshold.
18. Engine speed less than threshold.
19. Vehicle speed less than threshold.
20. Threshold vehicle speed exceeded since last engine start.
21. Occupant sensing allow engine stop condition met.
22. OBD allow engine stop condition met.
23. Engine runtime greater than threshold.
24. Stop-Start "Off" switch not activated.
25. Flex fuel learn mode not active.
26. ABS brake event not present.

EVIC Pop Up Messages Displayed on the EVIC

- EVIC message states Stop/Start Autostop Active

No Chime.
Normal Use.
Pop-up maintained for 5 seconds.
Displays with green hard telltale.

Stop/Start To Restart Press

Single Chime.
Driver put gear shift in gear without using Clutch; customer needs to return to Neutral or fully depress clutch pedal.
Pop up maintained for 5 seconds.

Stop/Start Restart Required Fault Detected

Single Chime.
MIL or ESS system fault preventing safe state confirmation during autostop.

EVIC Pop Up Messages Displayed within EVIC "Ring" menu

Stop/Start Ready

Stop-Start conditions met to enable engine stop.

Stop/Start Off

Stop-Start turned off by the customer at the switch.

Stop/Start Not Ready

Stop-Start conditions are not met to enable engine stop (ex: HVAC settings, engine temperature, etc).

Stop/Start Not Ready Steering Wheel Turned

Stop-Start condition not met with steering wheel turned past calibrated angle.