GM Service Manual Online
For 1990-2009 cars only

Lumbar Support System Components

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

    • Lumbar Switch
    • Seat Lumbar Motor Assembly
    • Driver Seat Module
    • Passenger Seat Module
    • Seat Circuit Breaker

A51 Lumbar Support System Operation

Battery voltage is supplied to the lumbar switch through the power seat circuit breaker. While the switches are in an inactive state the switch contacts are closed to the switch ground circuit. When a switch is pressed to an active state the switch contact is closed to the battery voltage supply circuit. Each motor is controlled by the lumbar switch through 2 motor control circuits. The motors are bidirectional and the direction of motor rotation is determined by which of the motor control circuits is switched to battery voltage while the other remains grounded.

AR9 Lumbar Support System Operation

The seat module supplies the lumbar adjuster switch assembly with a battery positive reference voltage. While the switches are in an inactive state the switch contacts are closed to the switch ground circuit. When a switch is pressed to an active state the switch contact is closed to the reference voltage circuit. Battery voltage on a switch signal circuit indicates to the seat module the switch status is active. Each seat adjuster motor is controlled by the seat module through 2 motor control circuits. While the seat adjuster motors are in an inactive state the motor control circuits are closed to ground circuit contacts within the driver seat module. The seat module operates the seat adjuster motors by switching one of a motor's control circuits to battery voltage. The seat adjuster motors are bidirectional and the direction of adjuster motor rotation is determined by which of the adjuster motor control circuits is switched to battery voltage while the other remains grounded.

The driver seat lumbar adjuster motors are equipped with internal position sensors. The adjuster motor position sensors are monitored by the driver seat module and are used to determine the lumbar positions when storing or recalling memory settings. The lumbar adjuster motors use potentiometer type position sensors. The position sensors are supplied with 5-volt reference and ground circuits from the driver seat module. The position sensor signal circuits are supplied 5 volts through a resistor them monitored within the driver seat module. The signal voltage monitored by the driver seat module ranges from 0.39 - 4.58 volts and is determined by the wiper location on the resistor within the position sensor. The signal circuit voltage levels are used by the driver seat module to determine the lumbar motor positions when storing or recalling memory seat position settings.