Seats: Description and Operation
POWER SEAT SYSTEM
The power seat system allows the driver and front seat passenger to electrically adjust their seating positions using the power seat switches located on the outboard seat cushion side shield of each front seat.
A driver side eight-way power seat is standard on highline models and optional on others. The power seat includes a six-way adjustable seat cushion track and a two-way power seat back. The eight-way power seat is also available with the heated seat and memory seat system that automatically positions the power seat for two different drivers.
The power seat system for this vehicle includes the following major components:
- Power Seat Adjuster - Depending on the seat, four-way or eight-way power, the adjuster (6) may be equipped with up to four electric motors.
There are three reversible motors that operate the power seat adjuster. The motors are connected to worm-drive gearboxes that move the seat adjuster through a combination of screw-type drive units.
The front and rear of a seat are operated by different motors. They can be raised or lowered independently of each other. When the center seat switch is pushed in the Up or Down direction, both the front and rear motors operate in unison. The forward/rearward motor is operated by pushing the center seat switch in the Forward or Rearward direction, which moves the entire seat in the selected direction on all models.
Each motor contains a self-resetting circuit breaker to protect it from overload. Consecutive or frequent resetting of the circuit breakers must not be allowed to continue, or the motors may be damaged.
The power seat adjuster cannot be repaired, and is serviced only as a complete unit.
- Power Seat Recliner - The power seat recliner (3) replaces the manual seat recliner. The power seat option includes an electrically operated power seat back recliner mechanism. The power seat recliner switch is integral to the power seat switch assembly, but is actuated with a separate switch knob. The power seat recliner motor assembly is mounted in the place of a seat hinge on the outboard side of the seat. The upper hinge plate of the power seat recliner mechanism is secured with two screws to the seat back frame and is concealed beneath the seat back trim cover and padding. The lower hinge plate and the motor and drive unit of the power seat recliner mechanism is secured with two screws to the seat cushion frame, and is concealed by the outboard seat cushion side shield.
The power seat recliner motor cannot be repaired. If the unit is faulty or damaged, it must be replaced.
- Power Seat Switches - Two power seat switches are used per vehicle if equipped with power seats. One seat switch is used for each front seat. Each switch is mounted in the appropriate seat cushion side shield. Refer to the appropriate power seat switch later for additional information.
The power seat system receives battery current through a 40 amp fuse in the Power Distribution Center (PDC) and a 20 amp circuit breaker in the junction block so that the power seats remain operational, regardless of the ignition switch position.
When a power seat switch is actuated, a battery feed and a ground path are applied through the power seat switch contacts to the appropriate motor or motors. The motor and drive unit operate to move the seat in the selected direction until the switch is released, or until the travel limit of the power seat track is reached. When the switch is moved in the opposite direction, the battery feed and ground path to the motor is reversed through the switch contacts. This causes the motor to run in the opposite direction.
When the recliner switch control knob is actuated, a resistance signal is sent to the appropriate Door Module via hard wired connections. The door module then sends the request to the Memory Seat Module (MSM) via the Controller Area Network (CAN) bus circuit. The MHSAPM is responsible for the 12v battery feed and ground path to the power seat recliner adjuster motor. The adjuster motor operates to move the recliner mechanism through its drive unit in the selected direction until the switch is released, or until the travel limit of the adjuster is reached.
The driver side power seat recliner motor used on models equipped with the memory system also has a position potentiometer integral to the motor assembly, which electronically monitors the motor position.
MEMORY SEAT SYSTEM
An electronic memory seat system is available on certain models. The memory system is able to store and recall all driver side power seat positions, and the drivers side view mirror positions. The system can be set for two different drivers. On vehicles with a factory installed radio connected to the Programmable Communications Interface (PCI) data bus network, the memory system is also able to store and recall up to twenty radio station presets (ten AM and ten FM), also for two drivers. The memory system also will store and recall the last station listened to for each driver, even if it is not one of the twenty preset stations.
The memory system will automatically recall all of these settings when a button of the memory switch is depressed, or when the doors are unlocked using the Remote Keyless Entry (RKE) transmitter (if enabled). If the vehicle has more than two drivers the RKE transmitter recall of memory features can be disabled. This is a customer programmable feature of the overhead console.
The memory system also has a easy exit feature that will move the driver seat rearward 55 millimeters or to the end of its travel, whichever occurs first, when the key is removed from the ignition switch lock cylinder. This is a customer programmable feature of the overhead console.
The memory system includes the following components:
- Memory Selector Switch - located in the driver door trim panel.
- Driver Memory Mirror Module (DMMM) - located in the driver door, behind the trim panel.
- Passenger Memory Mirror Module (PMMM) - located in the passenger door, behind the trim panel.
- Position Potentiometers - Drivers Mirror - The potentiometer is permanently installed on the drivers side view mirror motor. This potentiometer is used to provide a reference signal to the memory heated seat mirror module, letting the module know the exact position of the mirror.
- Sentry Key Remote Entry Module (SKREEM) - located at ignition key cylinder.
- Remote Keyless Entry (RKE) Transmitter - located with ignition key.
- Memory Seat Module (MSM) - located underneath the driver seat and also controls the Adjustable Pedals.
- Position Potentiometers - Seat Track - These potentiometers are permanently installed in each of the power seat track motors. They are used to provide a reference signal to the memory heated seat mirror module, letting the module know the exact position of the seat cushion and recliner.
- Radio - located in the instrument panel center stack.
- Automatic Temperature Control (ATC) - located in the instrument panel center stack.
Certain functions and features of the memory system rely upon resources shared with other electronic modules in the vehicle over the Controller Area Network (CAN) bus. The CAN bus allows the sharing of sensor information. This helps to reduce wire harness complexity, internal controller hardware, and component sensor current loads. At the same time, this system provides increased reliability, enhanced diagnostics, and allows the addition of many new feature capabilities. For diagnosis of these electronic modules or of the CAN bus, the use of a scan tool and the proper diagnostic information are needed.
The Memory Seat Module (MSM) receives hard wired inputs from the memory set/position switch and the potentiometers, mounted on each of the driver power seat adjuster motors and the driver side view mirror motor. The programmed software in the module allows it to know where the seat/mirror is located in its designed travel by a resistance reading generated from the seat adjuster or mirror mounted potentiometer. This way, when the memory switch is depressed the module will power the seat adjuster or mirror motors until the correct preset location is achieved. The module will prevent the seat memory recall function from being initiated, if the transmission gear selector lever is not in the Park or Neutral positions, or if the vehicle is moving. These inputs are monitored over the Controller Area Network (CAN) bus circuit by the MSM.
A memory setting is saved by pressing the "set" button, then pressing either the memory "1" or "2" button within 5 seconds of pressing the "set" button.
A memory setting is recalled by pressing either the memory "1" or "2" button, or by pressing the unlock button on a "linked" Remote Keyless Entry (RKE) transmitter.
For driver safety, memorized settings can not be recalled if the transmission is in a position other than Park or the seat belt is latched.