GM Service Manual Online
For 1990-2009 cars only

Caution: There is something about the vehicle that can make it move suddenly, and you or others can be seriously injured. This can happen if the vehicle is in the Auto Stop mode, and the shift lever is in D (Drive). Because the vehicle has the Automatic Engine Start/Stop feature, the vehicle's engine might seem to be shut off when you come to a complete stop. However, if you then start to exit the vehicle, as soon as you take your foot off the brake pedal, the engine will start again and the vehicle can move forward. If you are going to exit the vehicle, first shift to P (Park) and turn the ignition to LOCK/OFF. Then exit.

Your vehicle has an automatic engine start/stop feature. This feature can cause the engine to turn off when you are applying the brake and going less than 13 mph (21 km/h), or when you come to a complete stop. When you take your foot off the brake pedal, the engine will start again and you will continue forward. However, if you are on an incline, your vehicle may roll backwards a short distance until the engine performs the auto start. To be sure your vehicle will not move or roll, always keep your foot firmly on the brake pedal until you are ready for the vehicle to move.

Start the engine just as you would any normal engine. Also see "Starting Your Engine" in the Index of the owner manual for more information on starting. After the engine is started and has reached operating temperature, it will shut off automatically when bringing the vehicle to a stop -- usually the engine will shut off before a complete stop if you are braking at speeds below about 13 mph (21 km/h). If you are pulling a trailer and your trailer is equipped with trailer brakes, see Towing a Trailer for more information.

To restart the engine during the auto stop, release the brake pedal and the engine will start immediately. The vehicle will operate as a normal vehicle, until the next stop.

Automatic Engine Start/Stop Override

The automatic engine start/stop override feature may cause the engine to remain running at a complete stop or may start the engine at a complete stop. The following are reasons why either of these conditions may be encountered.

The engine will stay running at a complete stop or will automatically start from a complete stop if:

    • The outside temperatures are high -- usually above 95°F  (35°C). The climate control system is working to cool the cabin in AUTO mode. See Climate Controls .
    • The climate control system is in front defrost mode. See Climate Controls .
    • You release the brake pedal in DRIVE (D) or THIRD (3) -- even slightly.
    • The shift lever is in NEUTRAL, REVERSE (R), SECOND (2) or FIRST (1).
    • The battery pack charge is low.
    • The tow/haul mode is active.
    • The transfer case is in 4LO.
    • Any door is opened while the vehicle is in PARK (P).
    • It is necessary to maintain 120-volt APO operation for loads >1kw.
    • The hood is not fully closed.

Manual Override System


Object Number: 865662  Size: B3

To manually override the automatic engine start/stop system, press the tow/haul switch, located on the end of the column shift lever.


Object Number: 805790  Size: A1

When the tow/haul mode has been activated, this light will come on in the instrument cluster.

This system disables the engine from performing the auto stop function. While not required, you might choose to use this during frequent start/stops, while driving on grades or in heavy traffic.

Press the tow/haul switch again, or turn the ignition off, to enable the auto stop function. The indicator light on the cluster will go out.

The diesel engine starts differently than a gasoline engine.

Caution: Do not use gasoline or starting aids, such as ether, in the air intake. They could damage the engine. There could also be a fire, which could cause serious personal injury.

Refer to the 2005 Duramax Diesel Engine Owner Manual Supplement, located in the glove compartment.