Workshop Repair and Service Manuals GMC SIERRA

05-09-40-002G Safety Belt Locking Conditions (Normal Operating Characteristics) - (Jun 18 2013) Primary Seat Belts


Subject:Safety Belt Locking Conditions (Normal Operating Characteristic)

#05-09-40-002G: Safety Belt Locking Conditions (Normal Operating Characteristics) - (Jun 18, 2013) Primary Seat Belts

Models: 2005-2014 GM Passenger Cars and Light Duty Trucks

This bulletin has been revised to add the 2013-2014 model years. Please discard CorporateBulletin Number 05-09-40-002F.

The purpose of this bulletin is to explain when the safety belts are supposed to lock.There are several different locking situations for both front and rear safety belts.

Overspool Lock

There is an unintentional locking condition that ALL safety belts from ALL manufacturersmay experience called “overspool lock.” If the webbing snaps back to the stowed positionrapidly enough, the retractor will lock with the belt fully stowed. This is more likelyto occur when customers “help” the belt to retract. Without the weight of the latchplate and friction to slow the retractive speed of the webbing, the higher than normalwebbingretraction speed that occurs engages the locking mechanism when a sudden stop occursat the end of web travel. Since the webbing is now fully loaded on the spool, theretractor cannot rewind itself further to release the locking mechanism. When thishappens, the occupant cannot extract the belt to wear it. DO NOT replace the retractor for this condition until first attempting to disengagethe locking mechanism by followingthe recommendation listed below.


Pull hard on the locked webbing and then release. The hard pull extracts a small amountof webbing from the retractor which, in turn, permits a small amount of retractionto occur when released. This is all that is needed to disengage the locking mechanism.The safety belt will now function properly.

Vehicle Sensing

This type of locking occurs in response to the vehicle under the following conditions:

The vehicle changes speed or direction abruptly (the vehicle goes into rapid accelerationOR rapid deceleration or there is aggressive cornering).It can also occur in a static condition when a vehicle is parked on a large slant(fore-aft or side-to-side), such as streets in San Francisco, California.It may also occur over rough road conditions where the retractor mechanism is bouncedinto a locked condition.

In all of these conditions, as long as tension is maintained on the webbing, the beltwill stay locked. When the tension is released, the belt retracts slightly, the lockbar disengages and the safety belt should return to normal function. Please informcustomers that may comment that “the belt locks intermittently” that this is the designintent and the belt is functioning properly.

Web Sensing

This type of locking occurs in response to the extraction of webbing. When the webbingreels out at an accelerated rate, it goes into lock mode and stays there until tensionis again released. To observe this condition, extract the webbing quickly. Customersmay refer to this condition as “intermittent lock-up” and encounter it when tryingto put the belt on too quickly.

Automatic Locking (ALR)

When the webbing is pulled all the way out, it automatically converts the retractorinto a cinch-down mode (i.e.

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