GM Service Manual Online
For 1990-2009 cars only

The driver and front passenger power seat systems each consist of the following components:

    • Seat Adjuster Switch
    • Seat Horizontal Motor
    • Seat Front Vertical Motor
    • Seat Rear Vertical Motor
    • Seat Recline Motor
    • MSM/LT FRT PWR SEAT Circuit Breaker 25 A
    • MSM/RT FRT PWR SEAT Circuit Breaker 25 A

Seat Adjuster Switch

Battery positive voltage is supplied at all times to the driver and front passenger seat adjuster switches from their respective Circuit Breakers that are located in the rear fuse block. Both seat adjuster switches are grounded through the switch ground circuit and G 300. The seat adjuster switches provide both power and ground to the selected seat motors.

Motors

All of the seat motors operate independently of each other. Each motor contains an electronic circuit breaker (PTC) that will reset only after voltage has been removed from the motor. There are four seat position motors. These are the horizontal motor, front vertical motor, rear vertical motor, and the seat back recline motor. The horizontal motor moves the entire seat forward and rearward. Both vertical motors run simultaneously when the seat switch is operated to move the entire seat up and down. Or they can be selected independently to vertically tilt the front or rear of the seat up and down. The recline motor moves the angle seat back forward and rearward.

Horizontal

When the seat switch is operated to move the entire seat forward, battery positive voltage is applied through the horizontal motor forward switch contacts and the horizontal motor forward control circuit to the motor. The motor is grounded through the horizontal motor rearward switch contacts and the horizontal motor rearward control circuit to the motor. The motor runs in order to drive the entire seat forward until the switch is released. Moving the entire seat rearward works similarly to moving the entire seat forward, except that battery positive voltage and ground are applied on opposite circuits causing the motor to run in the opposite direction.

Rear Vertical

When the seat switch is operated to tilt the rear of the seat up, battery positive voltage is applied through the rear vertical motor up switch contacts and the rear vertical motor up control circuit to the rear vertical motor. The motor is grounded through the rear vertical motor down switch contacts and the rear vertical motor down control circuit to the rear vertical motor. The motor runs in order to drive the rear of the seat up until the switch is released. Tilting the rear of the seat down works similarly to tilting the rear of the seat up, except that battery positive voltage and ground are applied on opposite circuits causing the motor to run in the opposite direction.

Front Vertical

When the seat switch is operated to tilt the front of the seat up, battery positive voltage is applied through the front vertical motor up switch contacts and the front vertical motor up control circuit to the front vertical motor. The motor is grounded through the front vertical motor down switch contacts and the front vertical motor down control circuit to the front vertical motor. The motor runs in order to drive the front of the seat up until the switch is released. Tilting the front of the seat down works similarly to tilting the front of the seat up, except that battery positive voltage and ground are applied on opposite circuits causing the motor to run in the opposite direction.

Entire Seat Up or Down

When the seat switch is operated in order to move the entire seat to the up position, battery positive voltage is simultaneously applied through the front and rear vertical motor up switch contacts and the front and rear vertical motor up control circuits to both vertical motors. The motors are grounded through the front and rear vertical motor down switch contacts and the front and rear vertical motor down control circuits to both vertical motors. Both motors run simultaneously in order to drive the entire seat up until the switch is released. Moving the entire seat down works similarly to moving the entire seat up, except that battery positive voltage and ground are applied on the opposite circuits causing the motors to run in the opposite direction.

Recline

When the seat recline switch is operated to move the seat back forward, battery positive voltage is applied through the recline motor forward switch contacts and the recline motor forward control circuit to the recline motor. The motor is grounded through the recline motor rearward switch contacts and the recline motor rearward control circuit to the recline motor. The motor runs in order to move the seat back forward until the switch is released. Moving the seat back rearward works similarly to moving the seat back forward, except that battery positive voltage and ground are applied on the opposite circuits causing the motor to run in the opposite direction.