Seats: Description and Operation
POWER SEATSPower 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. 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.
WARNING: SOME VEHICLES ARE EQUIPPED WITH SEATBACK MOUNTED AIRBAGS. 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 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. Refer to Heated Seat System for more information on the heated seat option. Refer to Memory System in the Memory System section of this group for more information on the memory system.
The power seat system includes the following components:
- Power seat recliner
- Power seat switch
- Power seat track.
The power seat system with memory and heated seat options includes the following components:
- Power seat recliner
- Power seat switch
- Power seat track.
- Memory Heated Seat Module (MHSM)
- Memory set switch
- 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 allows the driver and/or front passenger seating positions to be adjusted electrically and independently using the separate power seat switches found on the outboard seat cushion side shield of each front seat. See the owner's manual in the vehicle glove box for more information on the features, use and operation of the power seat system.
Memory Seat System
An electronic memory and heated seat 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 power mirror positions for two drivers. For vehicles with a radio and heated I memory seat system connected to the Programmable Communications Interface (PCI) data bus network, the memory system is also able to store and recall up to twenty - ten AM and ten FM - 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 twenty preset stations.
The memory system will automatically return to all of these settings when the corresponding numbered and button of the memory switch on the driver side seat side shield is depressed, or when the doors are unlocked using the Remote Keyless Entry (RKE) transmitter. A customer programmable feature of the memory system allows the RKE recall of memory features to be disabled in cases where there are more than two drivers of the vehicle.
The memory system also has a customer programmable easy exit feature that will move the driver seat rearward 55 millimeters (two inches) or to the end of its travel, whichever occurs first, when the key is removed from the ignition switch lock cylinder.
A Memory Heated Seat Module (MHSM) is used on some models to control and integrate the many electronic functions and features included in the memory I heated seat system.
The memory system includes the following components:
- Memory heated seat module (MHSM)
- Memory set/selector switch
- Position potentiometers on both outside power mirrors
- Position potentiometers on the driver side power seat track and power seat recliner motors.
- Radio receiver (if Pd data bus capable).
Certain functions and features of the memory system rely upon resources shared with other electronic modules in the vehicle over the Programmable Communications Interface (PCI) 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. For diagnosis of these electronic modules or of the PCI data bus network, the use of a DRB scan tool and the proper Diagnostic Procedures are recommended.
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.
- Electronic Vehicle Information Center (EVIC) - Refer to Electronic Vehicle Information Center in Overhead Console Systems for more information.
- Powertrain Control Module (PCM) - Refer to Powertrain Control Module in Electronic Control Modules for more information.
- Radio Receiver - Refer to Radio Receiver in Audio Systems 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 Power Mirror in Power Mirrors for more information on the mirror position potentiometers. Refer to Power Seat Track and Power Seat Recliner in the Power Seat System section of this group for more information on the driver side power seat position potentiometers.
Refer to Power Seat in the Contents of Wiring Diagrams for complete circuit diagrams. Following are general descriptions of the remaining major components in the factory-installed memory system.
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 MHSM, 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 scan tool and the proper Diagnostic Procedures are recommended.
Electronic Vehicle Information Center
The Electronic Vehicle Information Center (EVIC) serves as the user interface for the memory I heated seat 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.
Fig. 1 Memory and Heated Seat Switches:
Memory Selector Switch:
MEMORY SET SWITCH
The memory selector switch is mounted on the drivers seat cushion side shield, within easy reach of the driver. This switch provides a way to set new and recall preset positions of seat, seat recliner, and the side view mirror. There are three separate switches incorporated into the memory set switch. The memory position set switch and memory position one and two switches.
The memory set switch cannot be repaired or adjusted. If one switch is damaged or faulty the entire memory set switch must be replaced.
When the memory set switch is depressed, a resistance multiplexed signal is sent to the memory/ heated seat module via hard wired connections. The memory/heated seat module than receives this hard-wired input and moves the power seat track/side view mirror according to the preset position. When the memory system is in set mode a chime will be generated by the body control module.
See the owner's manual in the vehicle glove box for more information on the features, use and operation of the memory switch.
DRIVER POWER SEAT SWITCH
Vehicles equipped with power seats utilize a eight-way driver power seat switch This eight way power seat switch features two knobs ganged together on the outboard seat cushion side shield.
The switch is secured to the back of the seat cushion side shield with two screws. However, the control knobs for the eight-way power seat switch unit must be removed before the seat switch can be removed from the side shield.
The power seat switch cannot be repaired. If one switch is damaged or faulty, the entire power seat switch assembly must be replaced.
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 power seat track or recliner adjuster motor. The selected adjuster motor operates to move the seat track or recliner through its drive unit in the selected direction until the switch is released, or until the travel limit of the adjuster 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 adjuster has reached its travel limit. The power seat adjuster motors 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. See the owner's manual in the vehicle glove box for more information on the power seat switch functions and the seat adjusting procedures.
PASSENGER POWER SEAT SWITCH
Vehicles equipped with power seats utilize a eight/ six-way passenger power seat switch. This eight/six-way power seat switch features two knobs ganged together on the outboard seat cushion side shield. Vehicles equipped with the eight-way, incorporate a power rear seat riser motor. Vehicles with the six-way do not.
The switch is secured to the back of the seat cushion side shield with two screws. However, the control knobs for the power seat switch must be removed before the seat switch can be removed from the side shield.
The power seat switch cannot be repaired. If one switch is damaged or faulty, the entire power seat switch assembly must be replaced.
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 power seat track or recliner adjuster motor. The selected adjuster motor operates to move the seat track or recliner through its drive unit in the selected direction until the switch is released, or until the travel limit of the adjuster 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 adjuster has reached its travel limit. The power seat adjuster motors 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. See the owner's manual in the vehicle glove box for more information on the power seat switch functions and the seat adjusting procedures.
POWER SEAT TRACK
The eight/six-way power seat options include a single electrically operated power seat track located under each front bucket seat. The power seat track unit replaces the standard equipment manual seat tracks. The lower half of the power seat track is secured at the front with two bolts to the floor panel seat cross member, and at the rear with two bolts to the floor panel. Four nuts secure the bottom of the seat cushion frame to four studs on the upper half of the power seat track unit.
The power seat track unit cannot be repaired, and is serviced only as a complete unit. If any component in this unit is faulty or damaged, the entire power seat track unit must be replaced.
The power seat track unit includes two/three reversible electric motors that are secured to the upper half of the track unit. Each motor moves the seat adjuster through a combination of worm-drive gearboxes and screw-type drive units. Each of the driver side power seat track motors used on models equipped with the optional memory system, also has a position potentiometer integral to the motor assembly which electronically monitors the motor position.
The front and rear (if equipped) of the seat are operated by two separate vertical adjustment motors. These motors can be operated independently of each other, tilting the entire seat assembly forward or rearward; or, they can be operated in unison by selecting the proper power seat switch functions, which will raise or lower the entire seat assembly. The third motor is the horizontal adjustment motor, which moves the seat track in the forward and rearward directions.