Principles of Operation
Seats
Principles of Operation
Driver and Passenger Power Seats Without Memory
The 6-way power seat feature moves the seat in 6 possible directions: the seat can be moved forward or backward and the front and back of the seat track can be moved up and down independently. The power seat feature operates independent of the ignition switch position.
The power seat motors are hardwired to the seat control switch. The circuits are normally at ground through the seat control switch. An individual circuit is switched to voltage when a specific adjustment position is selected.
Power Driver Seat With Memory
NOTE: A memory recall in progress does not prohibit the initiation of another memory recall; the most recently requested memory recall will be executed.
The driver power memory seat is controlled by the Driver Seat Module (DSM). The memory seat feature allows the driver to program a personalized seat position that can be recalled using the memory switch or a Remote Keyless Entry (RKE) transmitter. There are 2 memory settings possible. The exterior mirror and adjustable pedal positions are also stored and recalled with the driver memory seat positions.
For information on programming memory positions or recalling a stored memory position, refer to Memory Position Programming Programming and Relearning. For information on RKE transmitter programming or to diagnose a concern, refer to Doors, Hood and Trunk &/or Locks.
The DSM is located underneath the driver seat. Programmable Module Installation (PMI) must be carried out when installing a new DSM. Refer to Information Bus. The DSM does not require calibration to the driver seat track, although soft stops must be set within the seat track physical limits. Refer to Driver Seat Module (DSM) Hard Stop/Soft Stop.
The driver seat control switch provides voltage to the DSM when activated. The NEUTRAL position of the driver seat control switch position is a ground state through the seat control switch contacts. A voltage input causes the DSM to power the appropriate motor until the input is removed. Ground is the normal state of the motor circuits through the DSM and is not switched to control the motors. The DSM internally switches the appropriate circuit from ground to voltage for operating the motors.
As the seat is adjusted, the DSM constantly monitors the motor position sensors to record the current seat position. The DSM will remove voltage from the motor upon termination of the seat control switch input or if the DSM does not see movement from the motor by monitoring the position sensor.
The DSM has the ability for soft stops both at the upper and lower limits on all axis of the driver seat. When an axis reaches the hard stop and the switch is held for approximately one second, it will then back up 180 ms and establish the soft stop for that axis in that direction. The DSM uses this 'back up' strategy to check sensor integrity any time movement has stopped prematurely due to a sensor failure or obstruction.
The DSM communicates DTCs and other information using the MS-CAN communication bus. It should be noted for diagnostics that because Controller Area Network (CAN) bus communication is more robust and reliable than other methods, it may be possible to have limited module communication with one of the CAN bus circuits disconnected or shorted to ground. Refer to Information Bus for information concerning MS-CAN bus communication.
This only diagnoses concerns specific to the memory seat. To diagnose a memory exterior mirror concern, refer to Mirrors. To diagnose a memory adjustable pedal concern, refer to Hydraulic System, Brakes &/or Brake Pedal Assy.
Remote Keyless Entry (RKE) Transmitter
A RKE transmitter can be used to recall previously set memory positions but must first be associated to that memory position. The transmitter associated with personality 1 is capable of recalling memory position 1 only. Similarly, the associated personality 2 transmitter can recall only memory position 2.
Memory recall occurs when the unlock switch is depressed on the RKE transmitter if it has been associated with a memory position. The second depression of the unlock switch, which unlocks passenger doors, does not initiate a memory recall.
For information on diagnosing a RKE concern or associating a RKE transmitter to a memory position, refer to Doors, Hood and Trunk &/or Locks.
Driver Seat Module (DSM) Hard Stop/Soft Stop
A hard stop occurs when one of the memory seat track axes physically reach the end of travel and can go no further. A soft stop occurs when the seat stops before physically reaching the end of travel. The hard stop is set by seat design and cannot be changed or adjusted. The soft stop is set by the DSM. The seat track axes are forward/rearward, front up/down and rear up/down. To prevent unnecessary stress on the seat and motors, the DSM will set soft stop positions, 2 for each moving axis. The DSM will use a preset distance from the hard stop to determine where the soft stop will occur. When an axis reaches the hard stop and the switch is held for approximately one second in the same direction, the DSM establishes the soft stop for that axis in that direction.
Setting the Soft Stop
NOTE: If a new DSM or driver seat track has been installed, all driver seat track soft stops must be reset.
Use the following procedure once a new seat track or DSM has been installed.
During the setting procedure, if the seat track stops before the end of travel has been reached, the DSM has stopped at a previously set soft stop. To set the new soft stop, release the seat control switch and press again in the same direction until the seat track stops at the hard stop for that given direction.
1. Turn the ignition key to the ON position.
2. Press the seat control switch horizontal button forward until the seat track stops.
3. Keep the horizontal button pressed forward for one second after the seat track reaches its forward end of travel. The horizontal forward soft stop has been set, release the switch button.
4. Repeat Steps 2 and 3 for all seat track axes in both directions.
Heated Seats
The HVAC module contains the heated seat control buttons and indicators. The heated seat system functions independently from the climate control system.
A heated seat relay is located underneath each heated seat cushion frame. There are 2 voltage supplies to the heated seat relay. Voltage is supplied from the Smart Junction Box (SJB) to each heated seat relay coil when the ignition is ON. Voltage is also supplied to the relay contacts from the SJB to supply voltage to the heater mats. The HVAC module supplies ground to the relay coil when a heated seat switch button is pressed to energize the relay. This closes the relay contact to supply battery voltage from the SJB to the cushion heater mat. The cushion and backrest heater mats are wired in series. The driver and passenger backrest heater mats are connected to a shared ground circuit.
Each cushion heater mat contains a non-serviceable thermostatic switch that closes when cold to complete the heater grid circuit and heat the seat. When hot, the thermostatic switch opens the heater grid circuit and allows the seat to cool. During normal operation, several minutes may be required before seat temperature is increased and several more minutes of cooling before the heater mats continue with heating. The heated seat indicator illuminates continuously while the thermostatic switch cycles open and closed.
The seat should be occupied to correctly test for normal operation. Temperature measuring devices do not provide an accurate method for testing heated seat operation as surface temperatures are subject to human and environmental characteristics. Correct testing requires heater mat resistance measurements which have tight tolerances affecting heat cycle time length.
The system will time out and deactivate after 10 minutes. The heated seat system time-out is a characteristic of the HVAC module.