GM Service Manual Online
For 1990-2009 cars only

Power Seat System Components

The power seat system for the driver and passenger consists of the following components:

    • Power Seat Switch
    • Seat Horizontal Motor
    • Seat Front Vertical Motor
    • Seat Rear Vertical Motor
    • Seat Recliner Motor (Full Feature Seat Only)
    • Memory Seat Module (Drivers Full Feature Seat Only)

Power Seat System Operation

There are 2 options of power seats available with this system. One option is the base power seat and it is limited to positioning the seat vertically and horizontal only. The other option is a full feature seat that can position the seat vertically, horizontally and reclining the back cushion. The Power Seat System can contain up to four motors for positioning. They are the Horizontal, Rear Vertical, Front Vertical and Recliner motor. The Horizontal motor is used to position the seat horizontally while the Front Vertical and Rear Vertical motor can raise the whole seat up or down. The Front Vertical and Rear Vertical motors can be operated independently of each other so that the seat cushion can be tilted forward and rearward. The Recline motor (only found in the Full Feature Seat) positions the back of the seat forward or backward. Battery positive voltage is supplied to the Power Seats through the seat circuit breaker then to the Memory Seat Module and the Power Seat Switch (Full Feature Seat) or just to the Power Seat Switch (Base Seat). A ground circuit is supplied to the Power Seats at each individual seat and the motors can have ground applied to either control circuit by either the Power Seat Switch (base seat) or the Memory Seat Module (Full Feature Seat).

Seat Control Motors

The seat is positioned by reversible DC motors. Each motor runs clockwise, or anti-clockwise, depending on the polarity of the applied DC voltage. Input to move the Power Seat is received from the Power Seat Switch. On the base seat, the input from the Power Seat Switch directly goes to the motor. On the full feature seat, the input from the Power Seat Switch goes to the Memory Seat Module and then the Memory Seat Module applies battery positive voltage and ground as necessary to position the seat. When battery positive voltage and ground are applied to the control circuits the motor is energized and will move the seat in one direction. When the battery positive voltage and the ground is reversed on the control circuits the motor will move the seat in the opposite direction. Each motor has a internal circuit breaker that will open either when the seat reaches its limit of travel or if the seat is obstructed from moving, and will reset when the motor is no longer being energize

Memory Seat Module (MSM)

Battery positive voltage is supplied through the seat circuit breaker to the MSM and to the Power Seat Switch (Full Feature Seat) or just to the Power Seat Switch (Base Seat). A ground circuit is normally supplied to the Power Seats Switch at each seat and the motors can have ground applied to either control circuit by either the Power Seat Switch for base seat or by MSM for Full Feature Seat. In response to a valid manual or memory switch command, the MSM will apply power to the selected motors within 150 ms. To limit peak power, MSM restricts the number of motors that can be turned on simultaneously to three motors. If the module detects all four switches at the same time, MSM turns on three seat adjusters axes: horizontal, front, and rear. If the user continues to hold all four switches, the MSM actuates the fourth motor only after one of the first three motors has reached its end motion. For a memory recall operation, the MSM first moves the horizontal, front, and rear motors first. If all four switches are still activated, MSM actuate the recline motor only when one of the seat adjuster axes has reached its end motion. In order to conserve battery power, the MSM enters automatic standby mode whenever the unit has been inactive for 16 seconds. In the standby mode, the MSM stores memory settings so that when it is awake again it knows where the seat is set.

Position Sensors

The MSM in the full feature seat incorporates two methods for sensing the position of the 4 axes of the seat system: three-wire Hall Effect Sensors on horizontal, front vertical, and rear vertical. And potentiometer on recline motor axis. The MSM provides five volts and return ground to all the motor position sensors.

Platform Interface Signals

IGNITION and PARK signal affect memory recall motions. The memory seat normally works if the car is in PARK. The memory recalling function must be inoperative if the car is in Neutral or Driving mode.

Power Seat Switch adjuster

The power seat switches are powered by the switch feed circuit provided by the MSM. Normally the contact in the switches are connected to a good ground. The seat switches are divided into two major groups: Six-Way, and Two-Way seat adjuster. Six-Way seat switch adjuster adjusts the seat in Horizontal forward and rearward, Front up and down, and Rear up and down. The Two-Way seat switch adjuster adjusts the seat to recline in forward and rearward direction. The switches are mechanized such that the user cannot simultaneously actuate a given seat axis in two opposite directions.

Memory Seat Switch

The memory seat switch assembly consists of three push-button switches: RCL 1, RCL 2, and SET. The memory switch feed terminals are connected to a source of battery positive outside the MSM. When one of the memory recall button switch is activated, the seat moves to the direction where it is set to. If any of the three memory seat is actuated before the seat reaches its intended position, the seat will stop. In order to set the seat to a certain desired position, first the seat will be moved manually to the position desired, and press the SET button followed by pressing one of the Recall buttons.