Power Seat Control Module: Description and Operation

Fig. 3 Memory Heated Seat/Mirror Module (MHSMM) Location:

MEMORY HEATED SEAT/MIRROR MODULE
There are three versions of the Memory Seat Module (MSM). The standard version of the MSM is used on vehicles that are not equipped with the optional heated seat system. A Memory Heated Seat/Mirror Module (MHSMM) is used on vehicles that are equipped with the heated seat system option. A third module, the Heated Seat Module (HSM), does not have any memory system capabilities and is only available on vehicles that are equipped with an optional heated seat system. Refer to Heated Seats for more information on the heated seat system option.

All three modules are packaged in an identical molded plastic housing which is mounted on a bracket that is located between the power seat track and the seat cushion frame under the forward edge of the driver side front seat cushion. The MSM or MHSMM is used to control all of the driver side power seat memory functions and features. The MSM or MHSM contains a central processing unit and interfaces with other electronic modules in the vehicle on the Programmable Communications Interface (PCI) data bus network.

For diagnosis of the MSM, MHSMM or the PCI data bus, a DRB III scan tool and the proper Diagnostic Procedures are recommended. The MSM or MHSM cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.

The MSM receives hard wired inputs from the power seat switch and the potentiometers on each of the driver side power seat motors. The MSM receives messages over the PCI data bus from the Body Control Module (BCM) and the Powertrain Control Module (PCM) (vehicle speed status). The programming in the MSM allows it to process the information from these inputs and send control outputs to each of the driver side power seat motors. The MSM will prevent the seat memory recall function from being initiated if the driver side seat belt is buckled, if the transmission gear selector lever is not in the Park or Neutral positions, or if the vehicle is moving. The module also controls the seat heaters and is connected to the seat harness by four connectors.