Principles of Operation

Seats

Principles of Operation


Power Driver Seat With Memory

NOTE: Verify good battery condition before diagnosing the memory seat system. Poor battery condition may interfere with memory seat operation, even if vehicle starting is possible.

NOTE: A memory recall in progress does not prohibit the initiation of another memory recall; the most recently requested memory recall will be executed.

NOTE: When installing a new Driver Seat Module (DSM), it is necessary to carry out Programmable Module Installation (PMI). Refer to Information Bus. Programmable Module Installation (PMI)

The memory driver seat feature allows the driver to program a personalized seat position that can be recalled using the memory SET switch or a Remote Keyless Entry (RKE) transmitter. There are 2 memory settings possible. The exterior mirrors and steering column positions are also stored and recalled with the driver seat positions. The memory seat and memory recall feature operate independent of ignition being on or off.

Driver seat positions that can be programmed and recalled are:

- Seat forward or backward (horizontal)
- Seat front up/down (front vertical)
- Seat rear up/down (rear vertical)
- Backrest forward or backward

The DSM does not require calibration to the driver seat track, although soft stops must be set within the seat track physical limits.

The driver seat control switch provides voltage to the DSM when activated. The neutral position of each driver seat control switch position is a ground state through the seat control switch contacts. A voltage input causes the DSM to output voltage to 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 communicates DTC and other information using the MS-CAN communication bus. It should be noted for diagnostics that 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 system only diagnoses concerns specific to the memory seat. To diagnose an exterior mirror concern, refer to Mirrors. To diagnose a power steering column concern, refer to Steering Column.

For information on programming memory positions or recalling a stored memory position, refer to Memory Position Programming Programming and Relearning.


Easy Entry/Exit Feature

The easy entry/exit feature is a function of the DSM. When the ignition key is removed or for vehicles equipped with passive entry/passive start, when the button is pushed to turn the ignition off, the driver seat moves backward a maximum of 51 mm (2 in) or to the soft stop and the power tilt/telescopic steering column moves all the way up and forward. The DSM will cancel this operation if a valid input command is received from the driver seat control switch, memory SET switch, exterior mirror control switch or steering column control switch.

The DSM will record the current seat and power tilt/telescopic steering column positions before powering the seat and column for an easy exit operation. When the key is inserted into the ignition lock cylinder or for vehicles equipped with passive entry/passive start, the ignition button is pressed, the recorded position will be used to return the seat and steering column to the previous position during easy entry operation. Easy entry operation will be cancelled if a valid input command is received by the DSM.

The feature can be turned on/off using the message center or enabled/disabled using the scan tool under module programming. When enabled, using the scan tool, the feature becomes a user accessible item on the message center allowing the user to turn the feature on/off. Refer to the Owner's Literature or Instrument Panel, Gauges and Warning Indicators for information on the message center.


Remote Keyless Entry (RKE) Transmitter

NOTE: A memory recall in progress does not prohibit the initiation of another memory recall; the most recently requested memory recall will be executed.

An 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 an RKE transmitter 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, backrest (recline) or power tilt steering column axes physically reach the end of travel and can go no further. A soft stop occurs when the seat or steering column stops before physically reaching the end of travel. The hard stop is set by seat or steering column design and cannot be changed or adjusted. The soft stop is set by the DSM. To prevent unnecessary stress on the seat, steering column and motors, the DSM will set up to 10 soft stop positions, 2 for each moving axis. The seat track axes are forward/backward, front up/down and rear up/down. The seat backrest axis is forward/backward and the steering column axis is up/down. 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, 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.


Setting the Soft Stop

NOTE: If a new DSM has been installed, all power driver seat and steering column soft stops must be reset. If a new seat track, recline motor or steering column has been installed, only reset the soft stops for that component being installed new.

Use the following procedure once a new seat track, recline motor, steering column or DSM has been installed.

During the setting procedure, one second after a seat track, seat backrest or steering column axis reaches its end of travel in either direction, the DSM will move the motor being used on that particular axis a small amount in the opposite direction of the way the switch is being pressed. Once the motor has moved the seat track, backrest or steering column this small amount, the soft stop is set and the switch can be released.

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 seat track will then move back a small amount. The horizontal forward soft stop has been set, release the switch button.

4. Repeat Steps 2 and 3 for all seat track and backrest axes in both directions.

5. Repeat Steps 2 and 3 for power tilt column (if equipped).


Power Lumbar

The 4-way power lumbar moves the lumbar in 4 possible directions: up/down and in/out. The power lumbar feature operates independent of the ignition position.

The power lumbar 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 power when a specific adjustment position is selected.

The driver seat power lumbar positions cannot be set or recalled using the memory feature. No sensors are provided for these positions.


Passenger Power Seat

The 12-way passenger seat control feature moves the seat in 12 possible directions:

- Seat forward or backward (horizontal)
- Seat front up/down (front vertical)
- Seat rear up/down (rear vertical)
- Backrest forward or backward
- Lumbar up or down
- Lumbar in or out

All 12 positions are controlled by one switch. The power seat feature operates independent of ignition being on or off.

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.


Climate Controlled Seat System

NOTICE: Avoid applying voltage directly to a Thermo-Electric Device (TED) for testing its operation. Doing so may cause damage to the TED.

NOTE: When installing a new Dual Climate Controlled Seat Module (DCSM), it is necessary to carry out Programmable Module Installation (PMI). Refer to Information Bus. Programmable Module Installation (PMI)

Both the driver and front passenger climate controlled seats are independently controlled by the DCSM mounted to the bottom of the passenger seat cushion. The climate controlled seat system only operates with the engine running above 350 rpm, however, if using a scan tool to command the DCSM, diagnostic testing can be carried out with the ignition ON and engine OFF. The DCSM does not time out, it must be turned off using the Front Controls Interface Module (FCIM) (with navigation) or HVAC module (without navigation) buttons. The DCSM receives voltage from the Battery Junction Box (BJB) on DCSM C3265a pins E and F. If one pin does not receive voltage, both seats will remain operational because the voltage supply circuits are internally connected in the DCSM.

If a fault occurs setting a DTC specific to either climate controlled seat, only the affected seat will be disabled by the DCSM. If the system shuts down due to a fault, cycling the ignition OFF and then ON again will reset the DCSM to function until the fault reoccurs.

The 4 buttons (identified with seat icons) located on the FCIM (with navigation) or on the HVAC module (without navigation), cycle the DCSM. With each button push, the DCSM goes from off to high, medium, low and back off again. The indicators illuminate on each button to indicate the operating mode, 3 for HIGH, 2 for MED or 1 for LOW. The buttons with the blue seat icon operate the seat cooling mode and the buttons with the red seat icon operate the seat heating mode. The climate controlled seat system is not equipped with auto-mode.

Each driver and front passenger seat cushion and backrest is equipped with a Thermo-Electric Device (TED) and blower motor assembly. Applying voltage polarity to the TED in one direction causes it to heat. Applying voltage polarity in the opposite direction causes the TED to cool. Cabin air is drawn through the blower and distributed to each of the TED modules. The TEDs then heat or cool the incoming air depending on the control button settings. The air is then directed into the manifold where it is distributed along the surface of the cushion and backrest of the seat. Once activated, the DCSM maintains the heating/cooling modes until deactivated or a fault is detected.

The temperature differences between the individual heated and cooled settings is minimal. For example, it is difficult to distinguish between LOW COOL and MEDIUM COOL settings. Measuring seat temperature at different settings is possible by monitoring the DCSM PIDs using the scan tool.

When equipped with navigation, climate controlled seat button commands are communicated from the Front Controls Interface Module (FCIM) over the Medium Speed Controller Area Network (MS-CAN) to the HVAC module and then to the DCSM. Upon receiving a command, the DCSM then communicates indicator illumination commands back to the HVAC module which then commands the FCIM to turn the indicators on or off. No direct connection exists between the FCIM, HVAC module and DCSM. The climate controlled seat system can only operate if all 3 modules are communicating correctly on the Controller Area Network (CAN).

When not equipped with navigation, climate controlled seat button commands are communicated from the HVAC module over the MS-CAN to the DCSM. Upon receiving a command, the DCSM then communicates indicator illumination commands back to the HVAC module to turn the indicators on or off. No direct connection exists between the HVAC module and DCSM. The climate controlled seat system can only operate if both modules are communicating correctly on the CAN.

The MS-CAN bus is connected to the Data Link Connector (DLC) for diagnostic use. The climate controlled seats can be commanded using the diagnostic tool to verify both module communication on the MS-CAN bus and operation of the DCSM. This method may be useful for isolating a control switch concern. It should also be noted that because 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 additional information concerning CAN bus communication.


Heating Characteristics

- In heat mode, the TED circuits of a given seat are wired in parallel internally in the DCSM.
- In heat mode, the TED can add up to 40°C-60°C (72°F-108°F) to the ambient inlet air temperature as it passes over the TED.
- The system control settings are based on the 3 indicators on each climate controlled seat heat switch button. The first setting is HIGH (3 indicators), the second setting is MED (2 indicators) and the third is LOW (1 indicator) then OFF (no indicators).
- In the LOW setting, the DCSM is set to maintain TED temperature at approximately 46°C (115°F).
- In the HIGH setting, the DCSM is set to maintain TED temperature at 65°C (149°F).
- When heating, the DCSM will vary the speed of the fans and the TED duty cycle in order to reach and maintain the temperature determined by the switch setting (closed loop operation). Refer to the following table for heating mode temperatures.

NOTE: Temperatures are approximate.







Cooling Characteristics

- In cool mode, the TED circuits of a given seat are wired in series internally in the DCSM.
- In cool mode, the TED can remove up to 8°C (14°F) from the ambient air temperature entering the system.
- The system control settings are based on the 3 indicators on each climate controlled seat cool switch button. The first setting is HIGH (3 indicators), the second setting is MED (2 indicators) and the third is LOW (1 indicator) then OFF (no indicators).
- When cooling, the DCSM maintains constant speed of the fans and constant TED supply voltage (duty cycle) in open loop COOL mode (refer to the following table).





If the temperature at one of the TEDs falls below 5°C (41°F), the DCSM will shut down the TEDs and initiate system recovery mode. If the temperature continues to drop below 2°C (36°F), the DCSM will shut down the fans in the affected seat.


Climate Controlled Seat System Recovery Mode

NOTE: The presence of overtemperature faults (DTCs B2729, B2730, B272A and B272B) can be induced by incorrect operation of the climate controlled seat system after an initial heat setting has been attained. If a heat setting is repeatedly turned OFF and ON in an attempt to increase the seat temperature or repeatedly toggled between heat and cool modes, an overtemperature condition can result and the DTCs will be set.

If the temperature at one of the TEDs rises above 110°C (230°F) in the heat mode or 65°C (149°F) in the cool mode for more than 4 seconds, the DCSM will record an overtemperature DTC, remove voltage from the TEDs and go into recovery mode (blower only) for 30 seconds to cool down the TEDs. The same will occur if a temperature difference of 60°C (108°F) or greater is seen between the backrest and cushion TEDs on either front seat. The DCSM will continue to monitor the TEDs while in recovery mode. If the temperature of the TEDs does not drop to 105°C (221°F) in the heat mode or 60°C (140°F) in the cool mode after 30 seconds, the system will continue to cool the TEDs in recovery mode for up to 5 minutes. If the TEDs cool down at anytime after 30 seconds, but before 5 minutes (checked at 4-second intervals), the system will operate as normal. An overtemperature DTC will still be recorded even if the system recovers and is operating normally. Recovery mode is more likely to occur during extreme cabin temperatures with significant seat back sunload. If the system does not recover within 30 seconds in heat mode or within 5 minutes in cool mode, the DCSM will disable that seat (fault mode) and remain off until the ignition is cycled. Also, if the DCSM detects temperature differential fault twice during the same ignition cycle, it will shutdown. When a fault causes a shutdown, the climate controlled seat indicators will turn off for the affected seat and that seat will not be operational until the next key cycle.


Heated Seats - Rear

Vehicles equipped with rear heated seats are equipped with a single-heated seat module to control both rear heated seats. The heated seat module is attached to the rear seat backrest frame. The heated seat switch buttons are located in the rear panel of the front floor console. When the heated seat switch is pressed a momentary ground signal is sent to the heated seat module. The heated seat module then supplies voltage to the heater circuit. The seat cushion and backrest heater mats are wired in series and supplied voltage by the same output. The heated seat module monitors inputs from a temperature sensor, located in each seat's cushion heater mat and maintains seat temperature by cycling the heater feed output as necessary to maintain the setpoint temperature. The heated seat module will send voltage to the separate indicator circuit at the heated seat switch to indicate an on state. The heated seat module will remain on until switched off or the ignition is set to OFF. The heated seat module does not time out.

The heated seat module does not report DTCs and does not communicate on any network. If a fault is detected the affected seat system will be disabled. The faults detected will be:

- a heater feed circuit short to battery, ground or open.
- sensor circuit short to battery or open.
- heated seat switch stuck closed to ground.
- heated seat switch low and high inputs shorted together.

To reset the module, cycle the ignition OFF and then ON. After the heated seat module has been reset, the module will return to an off state. The heated seat module does not report DTCs and does not communicate on any communication network.

A new heated seat module must be configured after installation for correct operation. Heated seat module configuration occurs automatically when the low heat mode button is pressed on either rear heated seat switch. Until the module is correctly configured, the heated seats will operate incorrectly from the high heat mode button on either heated seat switch by following a sequence of high, low and off with each button press. After the low heat mode button is pressed on either heated seat switch, the module will correctly configure and the system will operate correctly.