GM Service Manual Online
For 1990-2009 cars only

Seat Assembly Description and Operation

The eight-way electric adjustable driver and passenger seat has eight movements (front up and down, rear up and down, forward/rearward movement and seat-back recliner) and an EZ-entry feature.

Hook and Loop cover assemblies are fully serviced and attached in the groves of the seat pad and the corresponding cover.

The rear seat is a two-passenger design, with a unique construction and adjustable rear head restraints.

Important: Accessory and after market seat covers MUST NOT be fitted to any vehicle with side airbags unless approved by the manufacturer. Non-approved seat covers may inhibit the operation of the side airbag, reducing the protection otherwise provided to the occupants during a side-impact collision.

Before performing any service operation on a front seat assembly, ensure the SRS is disabled. Refer to SIR Disabling and Enabling in SIR.

General Description

The eight-way electric adjustable driver and passenger seat is controlled by two lift motor and gearbox assemblies for front up and down and rear up and down movements. Each function can be operated independently of the other, or operated together to raise or lower the complete seat assembly. In addition to the two motor and gearbox assemblies described previously, a forward/rearward movement motor drives two gearboxes which control seat forward or rearward positioning. The fourth motor controls the seat-back recliner position.

Each lift motor and gearbox assembly is bolted to the inboard side of the seat height adjust assembly. When the lift motor is operating, it drives the gearbox which draws in or extends out the mating worm shaft which in turn operates on a lever and cross-brace. The cross-brace is connected to another lever on the opposite side of the seat height adjust assembly and this allows the raising or lowering of that section of the seat. Reversing the polarity on the lift motor terminals causes the motor to operate in the reverse direction and the seat moves in the opposite direction.

To control seat forward/rearward movement, a worm shaft is attached to each seat rail with the movement motor and gearboxes attached to the seat height adjust assembly.

The seat-back recliner angle is adjusted by a recliner motor attached to the inner frame. The motor output shaft has a drive gear which is meshed with a driven gear attached to the seat-back frame. Motor operation causes rotation of the drive gear which turns the driven gear and seat-back frame, thereby altering the seat-back recliner angle. Reversing the polarity on the recliner motor terminals causes the motor to drive in the reverse direction and the seat-back moves in the opposite direction.

The front seat also incorporates an EZ-entry feature that provides a simple one touch mechanism to move the front seat and allow rear seat passengers to enter or exit the vehicle. A lever on the outer upper corner of the seat-back disengages the seat-back locking mechanism. An internal micro switch senses when the lever is operated and signals to the module that the EZ-entry feature has been activated. The operator must press and hold the seat return switch to move the seat forward. The seat forward and rearward position is monitored by a potentiometer (incorporated into the forward forward/rearward rearward drive motor) and recorded in the seat module. Once the seat-back is returned to the locked position, the operator must press and hold the seat return switch to move the seat rearwards. When the seat reaches the last recorded location, the aft movement will pause for approximately three seconds before continuing to the fully rearward position.

An internal occupant sensing mat is incorporated into the front seat cushions. The occupant sensing mat signals to the seat control module whenever the seat is occupied with a weight in excess of 15 kg. The module then prevents the seat from driving forward should the EZ-entry function be initiated.

The front seats contain a seat control module mounted under the lower side cover.

Front Seat Assembly

Important: For reasons of personal safety, the vehicle must only be driven when the seat is adjusted to the correct driving position. Do not adjust the driver seat when the vehicle is moving as the seat could move away from the driving position, causing loss of control.

A seat control adjustment switch is fitted to the outside of each seat frame. This switch assembly provides independent control of the seat-back recliner angle, front and rear cushion height (up and down movement) of the seat along with forward/rearward movement.

During seat adjustment, the drive motors will stop operating at end of travel via an internal thermal cut-out switch, even if the seat adjustment switch is held on.

The eight-way position switch is disabled during automatic movement requested by operation of the EZ-entry function. The switch will be enabled once the automatic movement is completed or cancelled. The eight-way position switch is monitored by the module during automatic movement, and if the switch is operated, the automatic movement will be cancelled and the seat will enter the manual mode.

Ez-Entry System Occupant Sensing Mat

The EZ-entry system provides a one touch mechanism to move the front seat and allow rear seat passengers to enter or exit the vehicle. The EZ-entry system comprises of An EZ-entry lever on the upper outer side of the front seat, a seat return button in the EZ-entry lever escutcheon, and an internal occupant sensing mat.

When the EZ-entry lever is un-latched, the seat-back collapses forward. If the seat return switch is pressed and held, the seat launches to the full forward position. The seat will return to the pre-launch position once the lever is latched (i.e. the seat-back is returned to the upright position) and the seat return switch is pressed and held.

If a passenger (or load in excess of 15 kg) is present in the seat or enters the seat while it is automatically moving, the movement will cease. If weight detection causes the EZ-entry function to cease, a period of one second must pass without weight before a restart will commence.

The occupant sensing mat is installed inside the front seat cushions. The occupant sensing mat is a pressure switch with a nominal high or open circuit condition with no weight on the seat. The resistance decreases as the weight is increased. An integral diode is provided within the occupant sensing mat and is used by the module to verify connection of the occupant sensing mat prior to the automatic forward movement of the seat during the operation of the EZ-entry function. The module will test the mat sensor for either line connected to ground or battery and/or either line circuit open.

Detection of weight over the occupant sensing mat (seat cushion) will cause the seat module to either cancel an automatic forward movement or prevent an automatic forward movement from commencing. The module should detect a minimum weight on the seat of 15 kg. NOTE: The occupant sensing mat is sealed inside the seat cushion and is only available as part of a cushion assembly.