For 1990-2009 cars

The memory seat system consists of the following components:

• | Memory Seat Switch

• | Seat Adjuster Switch

• | Seat Lumbar Switch

• | Memory Seat Module (MSM)

• | Seat Interface Module (SIM)

• | Seat Horizontal Motor/Sensor

• | Seat Front Vertical Motor/Sensor

• | Seat Rear Vertical Motor/Sensor

• | Seat Recline Motor/Sensor

• | Seat Lumbar Motor/Sensor

• | SEAT Circuit Breaker 20 A

### Seat Interface Module and Memory Seat Module

The seat interface module (SIM) serves as an interface to the memory seat module (MSM) for serial data communications. It communicates with the MSM through a UART serial data line while it communicates with the vehicle through the low speed GMLAN serial data line. When the scan tool is used to observe MSM DTC information or scan tool data parameters, the SIM retrieves the information from the MSM via the UART serial data line, then gateways the information via the GMLAN serial data line that is displayed on the scan tool.

The SIM also serves as an interface to the MSM for memory recall operations. For memory recall operation refer to Memory Functions below.

### SIM and MSM Power and Ground

Battery positive voltage is supplied at all times through the SEAT circuit breaker located in the I/P fuse block to the seat interface module (SIM). This voltage is used to power up SIM and the memory seat module (MSM). The MSM uses this voltage to apply power to the seat and lumbar motors. Ground for the SIM and MSM is provided at G304.

### Seat Adjuster Switch and Lumbar Switch

Battery positive voltage is supplied at all times to the seat adjuster switch and lumbar switch from the SEAT circuit breaker located in the I/P fuse block. When the seat or lumbar switches are pressed they send a 12 V signal to the MSM. The MSM then commands the selected seat or lumbar motor to move in response to the switch signal.

### Seat Motors

There are four seat motors and one lumbar that move the position of the seat. These are the seat horizontal motor, front vertical motor, rear vertical motor, recline motor and the lumbar motor. The horizontal motor moves the entire seat forward and rearward. The seat front and rear vertical motors may operate independently to tilt the front or rear of the seat cushion up and down. Or, both vertical motors can run simultaneously to move the entire seat up or down. The recline motor moves the angle of the seat back forward or rearward while the lumbar motor moves the lumbar support forward and rearward. Each motor contains a electronic circuit breaker (PTC), that opens in the event of a circuit overload and will reset only after voltage has been removed from the circuit.

All motors are reversible. For example, when the seat switch is operated to moved the entire seat forward, battery positive voltage is applied through the horizontal forward switch contacts and the power seat horizontal forward switch signal circuit to the MSM. In response to this signal, the MSM applies battery positive voltage through the driver seat horizontal motor forward control circuit to the horizontal motor. The MSM supplies ground to the motor through the driver seat horizontal motor rearward control circuit. The motor runs 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 the opposite circuits causing the motor to run in the opposite direction. All of the seat motors and the lumbar motor are powered this way.

### Position Sensors

The seat and lumbar motors are equipped with position sensors internal to the motor. The sensors are monitored by the MSM and are used to determine seat and lumbar positions when storing or recalling memory settings. The seat front vertical and rear vertical motors use 3 wire hall effect type position sensors while the seat horizontal and recline motors use 2 wire hall effect type position sensors. The lumbar motor is equipped with a 2 wire potentiometer type position sensor. The MSM supplies the 3 wire hall effect position sensors with a separate 5 V reference circuit and signal circuit while ground is provided at G304. The MSM supplies the 2 wire hall effect position sensors with a signal circuit while ground is also provided at G304. During seat motor operation, the hall effect position sensor provides a determined number of pulse signals for every revolution of the motor shaft. These pulse signals (Steps) range from 0 - 65,535. The MSM monitors the step values from the signal circuits to determine seat motor positions. The MSM supplies the lumbar sensor with a signal and low reference circuits. The signal circuit voltage ranges from 0.25 - 4.75 V which is determined by the wiper location within the sensor. The MSM monitors this voltage signal to determine the lumbar position. High scan tool step or voltage readings indicate forward or upward seat/lumbar positions while low voltage or step readings indicate rearward or downward seat/lumbar positions.

### Memory Functions

The current seat position may be recorded for 3 different drivers. To record a position, adjust the drivers seat to a comfortable position, then press and hold the appropriate button for 5 seconds, a double beep will sound each time a memory position is set. Once the MSM receives the memory set message, it records the steps/voltage from all seat/lumbar position sensors for the appropriate driver.

When a memory switch is pressed, battery voltage is applied through the switch contacts and the signal circuit to the SIM. The SIM interprets this signal then applies battery voltage through the appropriate signal circuit to the MSM indicating the memory request. In response to this signal, the MSM applies battery voltage to run the seat motors until the position sensor steps/feedback voltages equal the steps/feedback voltages stored in memory for the appropriate driver.

Memory recall will not work if the shift lever is out of NEUTRAL (N) or PARK (P).

### Memory Inhibit/Enable

The memory seat module receives the ignition switch signal and the gear selector position via serial data messages. When the gear selector is in the PARK position and ignition switch is in the ON or OFF position, memory record and memory recall functions are all allowed. When the ignition switch is in the ON position and the gear selector is out of the PARK position, only memory record is allowed, all other memory seat functions are not allowed.