Stop Start Operation Vauxhall

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Stop Start Operation Vauxhall

Stop/Start System Description and OperationTable 1: Autostop Enable Ambient and Engine Coolant Temperature Table

The Stop/Start System is used to improve fuel efficiency in stop/start driving. The vehicle automatically shuts down the engine in appropriate conditions at a traffic light, for example, resulting in zero tail pipe emissions and saving fuel which otherwise is used idling the engine when stationary. The engine instantly restarts when the driver is ready to move away.
As soon as the driver prepares to move away (depress the clutch pedal), the engine starts quietly and almost instantly; it only takes the system around 0.3 s to start the engine. The process is near unnoticeable, and happens before gear selection is completed.
To support the increased number of engine starts, the starter motor is upgraded with a high performance electric motor and a stronger pinion engagement mechanism with reduced noise levels.
Along with the upgraded starter motor, advanced battery technology is required to ensure the vehicles battery can handle the frequent charge and discharge cycles common with stop/start operation. There is an intelligent battery sensor connected to the battery which continually monitors the battery charge and healthy state. The engine control module (ECM) uses this information from the intelligent battery sensor to determine if the battery charge and health is sufficient for an Stop/Start condition.
The Stop/Start system can reduce fuel consumption and carbon dioxide (CO2) emissions by up to 5% in mixed driving conditions. In an urban environment and in heavy traffic with frequent stops the savings may increase to as much as 10%.
There are also sophisticated controls in place to help ensure the Stop/Start System does not compromise the needs of either the driver or vehicle. For the engine to shutdown, the vehicle must be below 3 km/h (5 MPH), the manual transmission in neutral and the clutch pedal fully released. To restart, the driver simply depresses the clutch pedal and the enhanced starter motor engages the engine, ready for when first gear is selected. When the engine has been shut down by the Stop/Start System, the tachometer needle will rest at the Autostop indicator icon (500 RPM point) indicating the engine has been shut down by the Stop/Start System.
To ensure neither the needs of the driver or vehicle are compromised the engine will not shut down in the following circumstances:
•  Ambient and coolant temperature correlation does not match specified values.

•  Ambient temperature is less than -10°C (14°F)

•  Battery temperature is less than 0°C (32°F) or greater than 55°C (131°F)

•  Driver seat belt is not fastened and the drivers door is not fully closed

•  Clutch or accelerator pedal is pressed

•  HVAC system demand is high

•  HVAC defrost has been selected

•  Battery charge is lowLikewise the engine will automatically restart if:
•  Driver door opened and driver seat belt unbuckled

•  Engine hood opened

•  Battery charge is low

•  HVAC demand increases

•  Vehicle speed increases

•  Brake booster vacuum has been reduced

•  Engine coolant temperature is greater than 125°C (257°F)

•  Economy mode turned OFF by driver

•  Autostop time exceeded 5 minWhen the Stop/Start System has shut down the engine, and the ambient temperature is below 15°C (59°F), the ECM will activate the Stop/Start auxiliary relay which controls the electric engine coolant pump motor to continually circulate the engine coolant through the engine while the engine is off. This is to ensure the engine and passenger compartment temperature is maintained while off. Once the Stop/Start System has restarted the engine, the ECM will turn off the electric coolant pump motor, thus allowing the engines internal coolant pump to circulate the engine coolant. The Stop/Start System is automatically activated each time the ignition switch is turned on, although there is an ECO Switch on the instrument panel to disable the system, if the driver so desires.

Autostop Criteria
The ECM will send an Autostop state message to the body control module (BCM) and shut down the engine when all of the following criteria is met. The BCM will transmit the Autostop state message to the instrument cluster which will display the Autostop indicator in the tachometer display.
•  Economy mode turned ON

•  Vehicle speed during drive cycle was greater than 3 km/h (2 MPH)

•  Ambient and engine coolant temperature correlation meets specified values.

•  Hood switch status is closed

•  Driver door status is closed

•  Driver seat belt status is buckled

•  Brake booster vacuum is greater than 45 kPa (7 PSI)

•  Clutch switch is fully released

•  Transmission neutral position switch indicates neutral

•  Vehicle speed is less than 5 km/h (3 MPH)

•  Engine speed is below 1 500 RPM

•  Engine coolant temperature is less than 120°C (248°F)

•  No A/C compressor request from HVAC (A/C or Defrost modes)

•  Battery voltage greater than 12 V

•  Battery state of charge greater than 75% (changes with state of health)

•  Diesel particulate filter regeneration is not active

Autostop Enable Ambient and Engine Coolant Temperature Table

Ambient Temperature

Coolant Temperature

Autostop Enable

less than -10°C (14°F)



-10°C (14°F)

60°C (140°F)


0°C (32°F)

50°C (122°F)


6°C (43°F)

40°C (104°F)


12°C (54°F)

30°C (86°F)


20°C (68°F)

18°C (64°F)


30°C (86°F)

18°C (64°F)


30°C (86°F)

18°C (64°F)



Autostart Criteria
The ECM will send an Autostart state message to the BCM. If all of the following conditions are true the ECM and BCM will restart the vehicle.
Driver Enabled Conditions that will enable Autostart:
•  Transmission in neutral, clutch partially or fully depressed

•  If transmission is in gear, clutch must be fully depressed in order for AutostartSystem Enabled Conditions that will enable Autostart as long as transmission is not in gear
•  Brake booster vacuum is less than 40 kPa (7 PSI)

•  Vehicle speed is greater than 10 km/h (4 MPH)

•  HVAC inside air temperature changes than 3°C (5°F) (with HVAC Automatic)

•  A/C compressor request from HVAC (A/C or Defrost modes)

•  Battery voltage less than 11 V,

•  Battery state of charge is less than 73% (changes with state of health)

•  Diesel particulate filter regeneration is requested

•  Economy mode turned OFF

•  Driver door status changes to open and driver seat belt status changes to unbuckled.

•  Hood switch status changes to open

•  Autostop time exceeded 5 minIf the crank time exceeds 2 s, a manual ignition switch restart will be necessary.

System Components
Engine Control Module (ECM)The engine control module (ECM) monitors the inputs from the engine coolant temperature (ECT) sensor, vehicle speed sensor (VSS), hood ajar switch, brake booster vacuum sensor, the clutch pedal position sensor, the manual transmission neutral position switch and engine speed to determine Autostart and Autostop conditions. The ECM also controls the auxiliary coolant pump motor.

Engine Coolant Temperature sensorThe ECT sensor is used to determine engine operating temperature.

Intake Air Temperature SensorThe ECM uses this sensor to monitor ambient air temperature. If too cold, the Autostop will not occur.

Inside air temperature sensorThe HVAC control module monitors the passenger compartment temperature sensor to determine the temperature inside the passenger compartment. The HVAC control module sends this temperature reading to the ECM on the data communication circuit. The ECM uses this temperature values to determine if a restart is requires based on the temperature inside the passenger compartment.

Vehicle speed sensorThe vehicle speed sensor is used to determine vehicle speed. If vehicle speed is detected above a calculated value during an Autostop condition, the ECM will start the engine.

Hood Ajar SwitchIf the hood switch is in the open position, the vehicle will not Autostop. If the hood is opened during Autostop, the vehicle will automatically restart.

Brake Booster Vacuum SensorThe ECM monitors vacuum in order to ensure proper power assist for the brake pedal. If the ECM determines vacuum is too low, it will restart the engine.

Clutch Pedal Position SensorThe ECM monitors the clutch pedal position sensor for partial and fully depressed conditions. A partially depressed clutch pedal will cause the ECM to restart the engine during an Autostop condition if the transmission is in the Neutral position If the transmission is determined to be in gear, the ECM will not restart the engine until the clutch pedal is fully depressed.

Neutral Position SwitchThe manual transmission neutral position switch is used to determine if the transmission is in gear. The ECM will not allow Autostop until the clutch is engaged, the transmission is in the neutral position and then the clutch is fully disengaged.

Coolant Pump MotorThe ECM will turn on the auxiliary coolant pump motor during Autostop to maintain engine operating temperature and also maintain HVAC temperature. Once the engine is running, the ECM will turn off the coolant pump motor.

Body Control Module (BCM)The body control module (BCM) monitors the ECO switch in order to enable or disable the system. It is also the master of the low speed communication bus and transfers the appropriate messages to the instrument cluster and the HVAC.

Intelligent Battery SensorThe BCM monitors the intelligent battery sensor for battery state of current, state of health, and battery charge via the data communication bus. If the battery is determined to be in poor state of health or having a low charge, the BCM will not allow the ECM to Autostop.

ECO SwitchThe ECO switch can disable the Autostart system if desired.

DC to DC ConverterThe DC to DC converter monitors battery voltage during Autostop and will maintain operating voltage to the radio, instrument cluster and instrument panel displays. Battery voltage will drop slightly during Autostop and the DC to DC converter will maintain a constant voltage to ensure proper operation of the driver informational displays.

Driver Door SwitchThe BCM monitors the driver door switch at all times. The BCM will not allow Autostop if the door is ajar and will Autostart if the driver door is opened and the seat belt unbuckled during Autostop.

Driver Seat Belt SwitchThe BCM monitors the driver seat belt switch at all times. The BCM will Autostart if the seat belt is unbuckled and the driver door opened during Autostop.

Instrument ClusterIn order to differentiate between a normal engine shut down (engine speed 0 RPM) and when the engine has been shut down by the Stop/Start System, the tachometer needle will rest at the Autostop indicator icon (500 RPM point) indicating the engine has been shut down by the Stop/Start System. Once the engine is restarted, or the ECO button has disengaged Autostop, the tachometer will function normally.

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