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 engage Autostart:

• Driver removes pressure from the brake or depresses the accelerator pedal while the vehicle is in the forward Drive gear

System Enabled Conditions that will engage Autostart

• Economy mode turned OFF
• Brake booster vacuum is less than 40 kPa (6 PSI)
• 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)
• Driver door status changes to open and driver seat belt status changes to unbuckled (not applicable to vehicles in North America)
• Hood switch status changes to open
• Autostop time exceeded 2 min

If the crank time exceeds 2 s, a manual ignition switch restart will be necessary.

Fig 1: Autostart System Block Diagram

Courtesy of GENERAL MOTORS COMPANY