Principles of Operation

Seats

Principles of Operation

Driver and Passenger Power Seats Without Memory

The 10-way power seat control feature moves the seat in 10 possible directions: the seat can be moved forward or backward and the front and back of the cushion can be moved up and down independently. The backrest of the seat can be moved forward and backward, and the lumbar can be moved in and out. All 10 positions are controlled by one switch. The power seat feature operates independent of the ignition position.

The 8-way power seat control feature moves the seat in 8 possible directions. It is like the 10-way power seat, less power lumbar.

The 4-way power seat control feature moves the seat in 4 possible directions: the seat can be moved forward or backward and the backrest of the seat can be moved forward and backward.

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: 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.

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 2 settings consist of 8 possible directions: the seat can be moved forward or backward and the front and back of the cushion can be moved up and down independently. The backrest of the seat can be moved forward and backward. Adjustable lumbar is not a memory option. The power seat feature operates independent of the ignition position.

The driver seat control switch provides voltage to the DSM (Driver Seat Module) 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 (Driver Seat Module) to power the appropriate motor until the input is removed. Ground is the normal state of the motor circuits through the DSM (Driver Seat Module) and is not switched to control the motors. The DSM (Driver Seat Module) internally switches the appropriate circuit from ground to voltage for operating the motors.

As the seat is adjusted, the DSM (Driver Seat Module) constantly monitors the motor position sensors to record the current seat position. The DSM (Driver Seat Module) will remove voltage from the motor upon termination of the seat control switch input or if the DSM (Driver Seat Module) does not see movement from the motor by monitoring the position sensor.

The DSM (Driver Seat Module) communicates DTCs and other information using the MS-CAN (Medium Speed Controller Area Network) 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 (Controller Area Network) bus circuits disconnected or shorted to ground. for information concerning MS-CAN (Medium Speed Controller Area Network) bus communication.

For information on programming memory positions or recalling a stored memory position, refer to Memory Position Programming Programming and Relearning. For information on RKE (Remote Keyless Entry) transmitter programming, refer to Doors, Hood and Trunk &/or Locks.

The DSM (Driver Seat Module) is located under the driver seat. To install a new DSM (Driver Seat Module) , refer to Driver Seat Module (DSM) . Programmable Module Installation (PMI) must be carried out when installing a new DSM (Driver Seat Module).

This section only diagnoses concerns specific to the memory seat. To diagnose a memory exterior mirror concern, refer to Mirrors.

Easy Exit/Easy Entry

The easy entry/easy exit feature is a function of the DSM (Driver Seat Module) that moves the driver seat backwards about 50.8 mm (2 in) when the ignition key is removed from the ignition. The DSM (Driver Seat Module) receives a key out command over the MS-CAN (Medium Speed Controller Area Network) communication network and powers the driver seat rearward. This function will not operate if the seat is less than the 50.8 mm (2 in) travel distance to the end of the track or the function has been disabled. The DSM (Driver Seat Module) will also cancel this operation if a valid input command is received from the driver seat control switch, memory SET switch or exterior mirror control switch.

The DSM (Driver Seat Module) will record the current seat position before powering the seat for an easy exit function. This recorded position will be used to return the seat to this position on the easy entry operation. During easy entry operation, the seat is returned to the position previous to the easy exit operation. Easy entry operation will be cancelled if a valid input command from the seat control switch, memory SET switch or exterior mirror control switch is received by the DSM (Driver Seat Module).

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

Heated Seats

When equipped with navigation, heated seat request and indicator messages are communicated between the Front Controls Interface Module (FCIM) and HVAC module over the Controller Area Network (CAN) , otherwise, heated seat request and indicator messages are always communicated between the HVAC module and heated seat module.

The engine must be running for the heated seat system to operate and it does not time out. The heated seat module supplies voltage to the heater mats. The heated seat module regulates seat temperature by monitoring a thermostat located in the cushion heater mat.

The heated seat module does not report DTCs and does not communicate on the communication network. If a fault is detected, the module will disable the affected seat(s) and indicator(s). After the fault is corrected, the heated seat module needs to be reset by cycling the ignition.

The heated seat module control circuits are monitored by the HVAC module and will set a DTC if a circuit fault is detected. Refer to the HVAC Module DTC Chart. HVAC Module DTC Chart

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 (Thermo-Electric Device).

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. Programming and Relearning

The driver and front passenger climate controlled seats are independently controlled by the DCSM (Dual Climate Controlled Seat Module). The climate controlled seat system only operates with the engine running, however, if using a scan tool to command the DCSM (Dual Climate Controlled Seat Module) , diagnostic testing can be carried out with the ignition ON and engine OFF. The DCSM (Dual Climate Controlled Seat Module) receives voltage from the Battery Junction Box (BJB) on DCSM (Dual Climate Controlled Seat Module) 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 (Dual Climate Controlled Seat Module).

If a fault is detected, only the affected seat will be disabled. If the system shuts down, cycling the ignition OFF and then ON again will reset the DCSM (Dual Climate Controlled Seat Module) to function until the DTC resets.

The 4 buttons (identified with seat icons), located on the FCIM (Front Controls Interface Module) , activate each seat system setting and illuminate indicators on each button to indicate the operating mode, 3 indicators for HIGH, 2 indicators for MED or 1 indicator for LOW. The push-buttons with the blue seat icon operate the seat cooling mode and the push-buttons with the red seat icon operate the seat heating mode.

The climate controlled seat button commands are communicated from the FCIM (Front Controls Interface Module) over the MS-CAN (Medium Speed Controller Area Network) to the HVAC module and then to the DCSM (Dual Climate Controlled Seat Module). Upon receiving a command, the DCSM (Dual Climate Controlled Seat Module) then communicates indicator illumination commands back to the HVAC module which then commands the FCIM (Front Controls Interface Module) to turn the indicators on or off. The climate controlled seat system can only operate if all 3 modules are communicating correctly on the CAN (Controller Area Network).

Each cushion and backrest is equipped with a Thermo-Electric Device (TED) assembly that includes a seat blower (fan motor, serviced as an assembly with the TED (Thermo-Electric Device)). Applying voltage polarity to the TED (Thermo-Electric Device) in one direction, causes it to heat. Applying voltage polarity in the opposite direction causes the TED (Thermo-Electric Device) to cool. Cabin air is drawn through the blower and distributed to each of the TED (Thermo-Electric Device) modules located in the seat cushion and backrest. The TEDs (Thermo-Electric Devices) then heat or cool the incoming air depending on the control switch 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 the system is activated, the DCSM (Dual Climate Controlled Seat Module) controls the heating/cooling modes and the blower speed dependant on the settings.

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 (Dual Climate Controlled Seat Module) PIDs using the scan tool.

The climate controlled seats can be commanded using the scan tool to verify both module communication on the MS-CAN (Medium Speed Controller Area Network) bus and operation of the DCSM (Dual Climate Controlled Seat Module). This method may be useful for isolating a control switch concern. It should also be noted that because CAN (Controller Area Network) bus communication is more robust and reliable than other methods, it may be possible to have limited module communication with one of the CAN (Controller Area Network) bus circuits disconnected or shorted to ground. for information concerning CAN (Controller Area Network) bus communication.

Heating Characteristics

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, an overtemperature condition can result and the DTCs will be set.

- In the LOW setting, the DCSM (Dual Climate Controlled Seat Module) is set to maintain TED (Thermo-Electric Device) temperature at approximately 46°C (115°F).

- In the MEDIUM setting, the DCSM (Dual Climate Controlled Seat Module) is set to maintain TED (Thermo-Electric Device) temperature at approximately 60°C (140°F).

- In the HIGH setting, the DCSM (Dual Climate Controlled Seat Module) is set to maintain TED (Thermo-Electric Device) temperature at approximately 65°C (149°F).

- When heating, the DCSM (Dual Climate Controlled Seat Module) will vary the speed of the fans and the TED (Thermo-Electric Device) duty cycle in order to reach and maintain the temperature determined by the switch setting.

- Engine must be running over 350 rpm and seat heating does not time out.

Cooling Characteristics

- In cool mode, the TED (Thermo-Electric Device) circuits of a given seat are wired in series internally in the DCSM (Dual Climate Controlled Seat Module).

- In cool mode, the TED (Thermo-Electric Device) can remove up to 8°C (14°F) from the ambient air temperature entering the system.

- When cooling, the DCSM (Dual Climate Controlled Seat Module) maintains constant speed of the fans and constant TED (Thermo-Electric Device) supply voltage (duty cycle) in open loop cool mode.

- Engine must be running over 350 rpm and seat cooling does not time out.

The climate controlled seat system is deactivated by one of the following actions:

- Selecting the HVAC module setting to manual OFF.

- Turning the vehicle OFF.

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 (Thermo-Electric Devices) falls below 5°C (41°F), the DCSM (Dual Climate Controlled Seat Module) will shut down the TEDs (Thermo-Electric Devices) and initiate system recovery mode. If the temperature continues to drop below 2°C (36°F), the DCSM (Dual Climate Controlled Seat Module) will shut down the affected seat operation.

If the temperature at one of the TEDs (Thermo-Electric Devices) 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 (Dual Climate Controlled Seat Module) will record an overtemperature DTC, remove voltage from the TEDs (Thermo-Electric Devices) and go into recovery mode (blower only) for 30 seconds to cool down the TEDs (Thermo-Electric Devices). The same will occur if a temperature difference of 60°C (108°F) or greater is seen between the backrest and cushion TEDs (Thermo-Electric Devices) on either front seat. The DCSM (Dual Climate Controlled Seat Module) will continue to monitor the TEDs (Thermo-Electric Devices) while in recovery mode. If the temperature of the TEDs (Thermo-Electric Devices) 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 (Thermo-Electric Devices) in recovery mode for up to 5 minutes. If the TEDs (Thermo-Electric Devices) cool down at any time 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 (Dual Climate Controlled Seat Module) will disable that seat (fault mode) and remain off until the ignition is cycled. Also, if the DCSM (Dual Climate Controlled Seat Module) 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.