Seats - Overview

PRINCIPLES OF OPERATION

Front Power Operated Non-Memory Seats

The driver's non-memory seat will operate in all ignition power modes. The passenger non-memory seat will only operate when the ignition is in power mode 6 (Ignition).

Power for front passenger seat operation is supplied from the AJB via a passenger seat power relay to the passenger seat control switch pack. Power for the driver's seat operation is supplied directly from the AJB to the driver's seat control switch pack. The front passenger and driver seat power supplies are controlled by the CJB. The seat switch pack directs the voltage to the relevant seat adjustment motor when a seat control switch is pressed. Two pins within each of the seat switch packs control the seat motors. Both pins are normally connected to ground.

The driver and passenger switch packs are also connected in circuit with a battery-saver timer relay that is located in, and controlled by the CJB. The battery-saver timer relay allows operation of the driver and passenger seat controls for 10 minutes after the engine is switched off, and the ignition is then selected to an appropriate power mode. The 10 minute timer is reset if the appropriate ignition power mode is retained and the driver's door is opened or closed. The driver and passenger seat operation is inhibited immediately following central locking of the vehicle.

Operating a seat motor control switch applies voltage to one of the pins while the other pin remains connected to ground. Operating the seat motor control switch in the opposite direction reverses the power and ground connections to the motor, allowing the motor pinion to rotate in the opposite direction. In the event that a motor seizes or sticks, an internal thermal cut-out switch will trip to remove voltage from the motor.

Driver's Power Operated Memory Seat

The driver's memory seat will operate when the ignition is in power modes 4 (Accessory) and 6 (Ignition), and will not operate during power mode 9 (Engine crank).

Power for the driver's memory seat operation is supplied directly from the AJB to the power seat module. The memory seat switch pack is connected to the power seat module that controls the operation and memory position of the individual seat motors. The power seat module is connected on the medium speed CAN bus to the CJB and the front LH and RH door control modules.

The power seat module is also connected in circuit with a battery-saver timer relay that is located within, and controlled by the CJB. The battery-saver timer relay allows operation of the seat controls for 10 minutes after the engine is switched off, and the ignition is then selected to an appropriate power mode. The 10 minute timer is reset if the appropriate ignition power mode is retained and the driver's door is opened or closed. The driver's seat operation is inhibited immediately following central locking of the vehicle.

Requests for memory exterior mirror movements for a memory recall are transmitted on the medium speed CAN bus by the power seat module to the front door control modules. The front door control modules directly control the memory store and recall positions for the memory exterior mirrors.

Power Seat Module

The power seat module features driver selectable functions, and automatic monitoring functions.

Driver Selectable Functions
^ Seat and exterior mirror memory recall
^ Immediate seat adjustment.

Seat and exterior mirror memory recall function

The memory recall function sets the driver's seat to a stored position, and is activated when a switch pack memory position button is pressed. When memory recall is initiated, only 2 seat adjustment motors will operate at any one time to limit the overall current consumption. To further minimize the current load as the motors energize, the initiation of each of the 2 operating motors is phased with a 10 millisecond delay. The cushion slide and backrest will move first, followed by the cushion height.

As soon as the seat switch pack memory position button is pressed, a message is transmitted by the power seat module on the medium speed CAN bus to the front door control modules. The door control modules then activate the memory recall positions for the exterior mirrors. The instrument cluster message center will display memory recall messages when a memory recall is activated.

The memory recall function operates with 2 separate modes; the operation of each mode is dependant on the vehicle status when the seat memory position button is pressed.

Memory recall operating modes:
^ One-touch mode
^ Proportional mode.

One-Touch Mode

When the vehicle is stationary and a switch pack memory position button is pressed, the memory recall function will operate in 'one-touch' mode. One touch mode allows the seat and exterior mirrors to immediately move to the requested stored memory position.

If a seat adjustment or memory position button is operated during memory recall 'one-touch' mode, the current memory recall will be cancelled and the seat (and exterior mirrors via the medium speed CAN bus) will immediately stop moving. The seat will then commence moving in the direction that corresponds to the pressed switch.

Memory recall is also immediately cancelled if the vehicle is driven from the stationary position before the seat has reached the requested memory position.

Proportional Mode

If the vehicle is already in motion when the switch pack memory position button is pressed, the memory recall function will operate in 'proportional' mode. Proportional mode recalls the seat (and exterior mirror) position for the duration that the memory switch is held in the pressed state. When the memory position button is released the memory recall will immediately stop, unless the seat has already reached the intended memory position.

In order to reach the intended stored memory position while the vehicle is moving, the memory position button must not be released until all seat, and exterior mirror movements are complete.

Immediate seat adjustment function

The immediate adjustment function is activated when a switch pack seat position switch (recline, slide or height) is operated.

Pressing any of the seat adjustment switches will initiate the corresponding direction motor to move the seat in that direction, until the switch is released. Only 2 seat motors will operate at any one time.

Automatic Monitoring Functions

The power seat module automatic monitoring functions are detailed as follows:
^ Stall detection mode
^ Sleep mode
^ Battery monitor mode.

Stall detection mode

A seat motor is deemed to have stalled if there is no change in the input that is received from the corresponding feedback sensor for 200 milliseconds, while that axis is being driven.

If a stall condition is detected by the power seat module then the drive to that axis is cancelled for the remainder of that memory operation (memory recall), or until the switch is re-selected (immediate seat adjustment).

For all seat motor manual movements during an immediate seat adjustment function, when a motor is driven and a stall occurs the power seat module records and stores the stall position (soft stop) that the stall occurred. If movement occurs beyond the stored soft stop stall position, then the stall position is erased from the power seat module memory. This will always allow movement past a previously recorded stall position once movement has been registered beyond that position (i.e. by pressing the switch for longer than 2 seconds).

If the motor movement has stopped due to a motor stall (seat obstruction for example), once the obstruction is cleared then that axis may be activated again to move past the new soft stop stall position by re-selecting the appropriate switch and pressing for longer than 2 seconds. If the switch is not operated to move the seat past the new soft stop position, this position will remain stored in the power seat module memory as the full axis movement.

If motor movement has stopped due to loss of sensor feedback (sensor or wiring failure) then that axis may be activated again to move past the stall position by re-selecting the appropriate switch and pressing for longer than 2 seconds. This allows control of the motor to be maintained if sensor feedback is lost.

Upon re-selection of movement, if sensor pulses are detected then the motor will continue to be driven until the switch is released or another stall condition is detected. If sensor feedback is not detected then the motor is only driven for 0.5 second and then stops, until the switch is released and then pressed again for longer than 2 seconds, when a further 0.5 second of activation is permitted and so on. This is known as 'inch mode'.

If there is a failure with the medium speed CAN bus network, the seat will operate in 'inch mode'.

NOTE: For diagnostic purposes, an indication of medium speed CAN bus disconnection is apparent if the seat is operating in 'inch mode' and either the seat control module, CJB or door control modules are not shown connected to the medium speed CAN bus.

Sleep mode

The power seat module features a sleep mode to reduce power consumption to the required minimum.

If the power seat module is being prevented from entering sleep mode due to motor movement, memory recall or switch pack operation, then the module will enter sleep mode when the current function has terminated.

NOTE: In the case of a memory recall, all memory recall operations are carried out before the power seat module enters sleep mode, and not just the current motor movement.

The power seat module will exit sleep mode when any CAN bus activity is detected.

Battery monitor mode

The power seat module monitors the input power supply to make sure there is sufficient battery voltage available for engine cranking. If the battery voltage drops below 10.5 volts, then the power seat module ignores all requests for a memory recall until the battery voltage is greater than 11.0 volts.

If the battery voltage drops below 8.5 volts, then the power seat module ignores all requests for seat movement until the battery voltage is greater than 9.0 volts.

If the battery voltage is greater than 16.5 volts, then the power seat module ignores all requests for seat movement until the battery voltage drops below 16.0 volts.