What's new

2021 Autostop


Dec 6, 2020
Reaction score
Woodstock, GA
I have a 2021 5.3 that came with the autostop feature. It does have a switch to turn it off. Seems to me that is extra wear and tear on the starter and everything else. What are your options on this feature?
Thanks! Spyder
Takes about 30 minutes to pop the console and center dash trim pieces off and install the device, then reinstall the pieces, but they have a great instruction video. It is helpful to have an interior pry tool, check eBay for them...about 4 bucks for a multi-tool kit!!
Yea, looked in depth. Wonder if I can just take the switch off and cross-connect the wire for permanent off.
Yea, looked in depth. Wonder if I can just take the switch off and cross-connect the wire for permanent off.
No need for all that; Just set it to off and it stays that way, or set it to on and it stays that way... works great !!
If anyone is interested this is what the 2021 Autostop specs are

This is a pinion spring mechanism starter design , listed below is the GM engineering explanation
All auto stop engines have polymer impregnated engine bearings

Stop/Start System Description and Operation (KL9)

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 (by releasing the brake pedal and/or depressing the accelerator pedal), the engine will start; it only takes the system around 0.3 s to start the engine.

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 5 km/h (3 MPH), the selector lever in position D, and brake pedal depressed. To restart, the driver simply releases the brake pedal and the enhanced starter motor engages the engine. When the engine has been shut down by the Stop/Start System, a control indicator will be illuminated in the Driver Information Center (DIC). When the engine is restarted, the control indicator in the DIC extinguishes.

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 (not applicable to vehicles in North America)
  • HVAC system demand is high
  • HVAC defrost has been selected
  • Battery charge is low
  • The learn procedure needs to be completed on the Battery Sensor Module
Likewise the engine will automatically restart if:

  • Driver door opened and driver seat belt unbuckled (not applicable to vehicles in North America)
  • 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 2 min
When 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.

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

Initial minimum vehicle speed during drive cycle must be 19 km/h (12 MPH) or greater. Subsequent autostop minimum speed may vary from 2-10 km/h (1-6 MPH), depending on vehicle

Ambient and engine coolant temperature correlation meets specified values.

Ambient and transmission fluid 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)

Transmission gear selector is in the Drive position

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)

Ambient temperature is greater than −10°C (14°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)

Autostop Enable Ambient and Engine Coolant Temperature Table​
Ambient Temperature
Minimum Coolant Temperature
Autostop Enable
−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)​
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

Note: If one or more of the following conditions occur, the system will force the engine to restart.

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.
Check out the Auto Stop Eliminator, I installed one and am very pleased!
Agreed 100%. I initially purchased a plug-in version, but didn't like how truck was in diagnostic mode. I saw your post and made the purchase. This is the best. Not a bad install, and works like the factory switch should.

Most Reactions

🔥 Amazon Favs 🔥

Latest Discussions...