GM Service Manual Online
For 1990-2009 cars only

Motors

The memory seat system consists of the memory seat module (MSM) and 4 seat motors. The MSM controls the movement of the 4 seat position motors. All the motors operate independently of each other. Each motor contains an electronic circuit breaker (PTC), which will reset only after voltage has been removed from the motor.

There are 3 motors that move the position of the seat. These are the forward/back motor, rear height motor, and front height motor. Both height motors run simultaneously when the left seat switch is operated in order to move the entire seat up and down. The recline motor moves the angle of the seatback.

All motors are reversible. For example, the seat is moved forward and back by one motor. When the MSM receives an input to move the seat forward, the MSM supplies battery positive voltage (B+) and ground to run the motor in order to move the seat forward. When the MSM receives a seat back input, the MSM will supply power to the same motor, but the voltage and ground will be on the opposite motor cavities. The voltage polarity is reversed and the motor will run the opposite direction, moving the seat back. All other seat motors are also powered this way.

The MSM provides each seat motor with a soft stop. The module will actually stop the motor just before the physical end-of-travel for that motor. This decreases the stress on each motor. If a motor reaches the end-of-travel due a soft stop and the seat switch is released and then activated again, the seat will move a short distance farther, to the physical travel limit.

Manual Movement

The memory seat module (MSM) receives the seat manual movement inputs from the left seat switch. When a forward/back, rear vertical, front vertical, or recline input is received, the MSM supplies battery positive voltage (B+) to the appropriate motor(s) and the seat or seatback moves accordingly.

Memory Inhibit/Enable

When the ignition switch is in the OFF position, memory record, memory recall, personalization recall, and exit recall functions are all allowed. When the ignition switch is in the ON position and the gear selector is in the PARK position, only the recall personalization function is deactivated and all other memory functions are allowed. When the ignition switch is in the ON position and the gear selector is out of the PARK position, memory record is allowed, but all other memory seat functions are not allowed.