System Description

POWER SEAT SYSTEM
The power seat system option allows the driver and front seat passenger to electrically adjust their seating positions for optimum control and comfort using the power seat switches located on the outboard seat cushion side shield of each front seat. Both power front seats can be adjusted in eight different directions up, down, front up, front down, rear up, rear down, forward, rearward and recliner forward and rearward.

The power seat system receives battery current through a 40 amp fuse in the Intelligent Power Module and a 30 amp circuit breaker under the seat so that the power seats remain operational, regardless of the ignition switch position.

Fig.1 Identifying A Side Airbag Equipped Seat:

WARNING: SOME VEHICLES ARE EQUIPPED WITH SEATBACK MOUNTED AIRBAGS (FIG. 1). BEFORE ATTEMPTING TO DIAGNOSE OR SERVICE ANY SEAT OR POWER SEAT SYSTEM COMPONENT YOU MUST FIRST DISCONNECT AND ISOLATE THE BATTERY NEGATIVE CABLE. THEN WAIT TWO MINUTES FOR THE SYSTEM CAPACITOR TO DISCHARGE BEFORE FURTHER SYSTEM SERVICE. THIS IS THE ONLY SURE WAY TO DISABLE THE AIRBAG SYSTEM. FAILURE TO DO SO COULD RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL INJURY.

A eight-way power seat is standard on highline models and optional on others. This option includes a eight-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. Refer to Heated Seats for more information on the heated seat option. Refer to Description Memory Seat System in this section for more information on the memory seat system.

The power seat system includes the following components:
- Power seat recliners
- Power seat switches
- Power seat tracks
- Circuit breaker

The power seat system with memory and heated seat options includes the following components:
- Power seat recliner
- Power seat switch
- Power seat track.
- Memory Seat Mirror Module (MSMM)
- Memory set switch
- Heated Seat Module (HSM)
- Heated seat switch
- Electronic Vehicle Information Center (EVIC)
- Programmable Communications Interface (PCI) data bus network

Refer to Wiring Diagrams for complete circuit diagrams. Following are general descriptions and operations for the major components in the power seat system and memory seat system.

The power seat system receives battery current through fuse # 22 in the Intelligent Power Module and a circuit breaker under the front seats, regardless of the ignition switch position.

When a power seat switch control knob or knobs are actuated, a battery feed and a ground path are applied through the switch contacts to the appropriate power seat track adjuster motor. The selected adjuster motor operates to move the seat track through its drive unit in the selected direction until the switch is released, or until the travel limit of the seat track is reached. When the switch is moved in the opposite direction, the battery feed and ground path to the motor are reversed through the switch contacts. This causes the adjuster motor to run in the opposite direction.

No power seat switch should be held applied in any direction after the seat track has reached its travel limit. The power seat track each contain a self-resetting circuit breaker to protect them from overload. However, consecutive or frequent resetting of the circuit breaker must not be allowed to continue, or the motor may be damaged. Refer to the owner's manual in the vehicle glove box for more information on the features, use and operation of the power seat system.

Memory System
An electronic memory system is available on some models. The memory system is able to store and recall the driver side power seat positions (including the power recliner position) and both outside side view mirrors positions for two drivers. On vehicles equipped with a factory radio, the memory system is also able to store and recall radio station presets 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 preset stations.

The memory system will automatically return to its preset settings when the corresponding numbered button of the memory switch is depressed, or when the doors are unlocked using the corresponding Remote Keyless Entry (RKE) transmitter. A customer programmable feature of the memory system allows the RKE recall of memory features to be disabled, if desired. This programmable feature is internal in the EVIC module, which is located in the overhead console.

A Memory Seat Mirror Module (MSMM) is used on some models to control and integrate the many electronic functions and features included in the memory seat and mirror systems.

The memory system includes the following components:
- Memory Seat Mirror Module (MSMM)
- Memory set switch
- Position potentiometers on both outside side view mirrors
- Position potentiometers on the driver side power seat track and power seat recliner motors.
- Electronic Vehicle Information Center (EVIC)
- Radio receiver (if PCI data bus capable).

Certain functions of the memory system rely upon resources shared with other electronic modules in the vehicle over the Programmable Communications Interface (PCI) J1850 data bus network. The PCI data bus network 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. Initial diagnosis of these electronic modules or the PCI data bus network requires the use of a DRB III scan tool and the proper Diagnostic Procedures manual. If this method does not prove conclusive, the use of a automotive meter such as the Fluke�, the proper wiring schematics and the service manual diagnostic routines are required.

The other electronic modules that may affect memory system operation are as follows:
- Body Control Module (BCM) - Refer to Body Control Module in Electronic Control Modules for more information.
- Powertrain Control Module (PCM) - Refer to Powertrain Control Module in Electronic Control Modules for more information.

Refer to Heated Seat System for more information on the heated seat system. Refer to Remote Keyless Entry System in Power Lock Systems for more information on the RKE system.

Refer to Wiring Diagrams for complete circuit diagrams. Following are descriptions, theory of operation, diagnosis/testing procedures and removal/installation procedures of the major components in the memory and power seat systems.

The memory system receives battery current through fuse # 22 in the Intelligent Power Module and the power seat system circuit breaker, located under each front seat near the rear edge of the seat cushion pans. The Memory Seat Mirror Module (MSMM) will drive a maximum of 2 motors at a time in a given direction. If conflicting directions are requested, the priority for response will be as follows:
- Seat Track Rearward or Forward
- Seat Front Down or Up
- Seat Rear Down or Up
- Recliner Rearward or Forward

The inputs from these switches to the MSMM is a current limited battery source fed by the MSMM. This protects the MSMM printed circuit board traces from acting as fuses. All of these switch contact inputs to the MSMM are normally closed to ground, except when actuated.

See the owner's manual in the vehicle glove box for more information on the features, use and operation of the memory system. For diagnosis of the MSMM, the PCI data bus, or the other electronic modules on the PCI data bus that provide inputs and outputs for the memory system, the use of a DRB III scan tool and the proper Diagnostic Procedures manual are recommended.

Electronic Vehicle Information Center
The Electronic Vehicle Information Center (EVIC) serves as the user interface for the memory system. It displays memory system status messages and provides the user with the means for enabling and disabling the many customer programmable features available on the vehicle, including those for the memory system.

See the owner's manual in the vehicle glove box for more information on the features, use and operation of the EVIC. Refer to Electronic Vehicle Information Center in Overhead Console Systems for more information on the EVIC.

MEMORY SYSTEM
The memory system consists of power driver's seat, power mirrors and radio presets. The Memory Seat/Mirror Module (MSMM) is located under the driver's seat. It receives input from the following: driver's manual 8-way seat switch, driver's seat position sensors, PCI bus circuits, and the power mirror sensors. The module uses these inputs to perform the following functions: position the driver's memory seat, both exterior mirrors (during recalls), and send/receive the memory system information over the PCI bus.

If any one of the memory controlled systems is inoperative from its manual switch, use the schematics and diagnostic information to correct the concern. This manual addresses the memory problems only and it is assumed there is not a basic component failure.

Power Seat
The memory power seat provides the driver with 2 position settings for the driver's seat. Each power seat motor is connected to the MSMM with two motor drive circuits. Each circuit is switched between battery and ground. By being able to bi-directionally drive the circuits, the MSMM controls the movement of the motors based on input from the power seat switch or from the position sensors when performing a memory recall. Each motor contains a potentiometer to monitor the seat position. To monitor the position of the motor, the MSMM sends out a 5-volt reference on the sensor supply circuit. The sensor is grounded back to the module on a common ground circuit. Based on the position of the sensor, the MSMM monitors the voltage change through the sensor on a separate signal circuit.

The MSMM stores the input value of each of the four seat potentiometers in memory when the system requests a set. The driver can initiate a memory recall, using either the door mounted memory switch or the RKE transmitter (if the remote linked to memory feature is enabled via the EVIC). When initiated, the MSMM adjusts the four seat sensors (by using the motors) to match the memorized seat position data.

For safety, the memory seat recall is disabled by the MSMM when the vehicle is out of park position or if the speed is not zero. Any obstruction to seat movement over a 2-second delay will cause the seat to stop moving in which case a stalled motor would be detected by the MSMM and the corresponding seat output would be deactivated. However, if the object obstructing the seat is removed, the seat will function normally again.

Memory Mirrors
Each outside mirror contains vertical and horizontal bi-directional drive positioning motors and position sensors. The MSMM provides a 5-volt reference on the signal circuit to each position sensor. The sensors share a common ground circuit. The MSMM monitors the position of the mirror motors by measuring the voltage on each signal circuit. When a memory position is set, the MSMM monitors and stores the position of the outside mirrors. The MSMM adjusts the mirrors to the appropriate positions when a memory recall message is received from the RKE or is requested from the memory set switch.

The power mirror switch during non-memory operation operates both mirrors independently of the MSMM.