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 sensor 

The ECT sensor is used to determine engine operating temperature.

Intake Air Temperature Sensor 

The ECM uses this sensor to monitor ambient air temperature. If too cold, the Autostop will not occur.

Inside air temperature sensor 

The 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 sensor 

The 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 Switch 

If 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 Sensor 

The 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 Sensor 

The 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 Switch 

The 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 Motor 

The 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 Sensor 

The 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 Switch 

The ECO switch can disable the Autostart system if desired.

Power Supply Transformer 

The 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 Switch 

The 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 Switch 

The 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 Cluster 

In 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.

Callout	Component Name
K9	K9 Body Control Module
S48A	S48A Multifunction Switch - Instrument Panel
K20	K20 Engine Control Module
B209	B209 Neutral Position Sensor