Principles of Operation

Seating

Principles of Operation

Driver and Passenger Power Seats Without Memory

The 14-way power seat track 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. The lumbar can be moved in and out, up and down or can massage. The seat cushion can also massage. All modes of operation are controlled by one switch. Refer to Seating for switch and system operation.

The 10-way power seat control feature moves the seat in 10 possible directions. It is like the 14-way power seat, less up and down power lumbar and massage.

The 6-way power seat control feature moves the seat in 6 possible directions. It is like the 10-way power seat, less power lumbar and recline.

The power seat track, recline and stand alone power lumbar motors operate independent of ignition position. Power lumbar with backrest and cushion massage require the engine to be running. The power seat motors and lumbar control module 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 MS-CAN (Medium Speed 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 MS-CAN (Medium Speed Controller Area Network) bus circuits disconnected or shorted to ground. Refer to Information Bus 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 Seats. Programmable Module Installation (PMI) must be carried out when installing a new DSM (Driver Seat Module).

This system only diagnoses concerns specific to the memory seat.

Easy Exit/Easy Entry

The easy entry/exit feature is a function of the DSM (Driver Seat Module). 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. 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. The DSM (Driver Seat Module) 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 adjustable pedal 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 when the key is inserted into the ignition lock cylinder or for vehicles equipped with passive entry/passive start, the ignition button is pressed. Easy entry operation will be cancelled if a valid input command is received by the DSM (Driver Seat Module).

The easy entry/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.

Driver Seat Module (DSM) Hard Stop/Soft Stop

A hard stop occurs when a memory seat track or backrest (recline) 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 (Driver Seat Module). To prevent unnecessary stress on the seat, the DSM (Driver Seat Module) 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. The DSM (Driver Seat Module) 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 (Driver Seat Module) uses this "back up" strategy to check sensor integrity any time movement has stopped prematurely due to a sensor failure or obstruction.

When a new driver seat track with memory or recliner motor, or a DSM (Driver Seat Module) has been installed, operate the seat in all directions through the full range of travel to set soft stops and avoid a premature stopping point occurrence after the vehicle is returned to the customer.

Power Lumbar With Cushion and Backrest Massage

Each front seat functions independently of each other. The lumbar control module is located in the seat backrest. The system will function only with the engine running. The lumbar control module does not report DTCs and does not communicate on the CAN (Controller Area Network). The button pushed on the seat control switch will determine what function the module will carry out. When an individual circuit is switched to voltage, the lumbar control module will carry out a function.

The pump supplies air pressure through a hose to the lumbar control module. The module then directs the air through multiple hoses to the appropriate cushion or backrest pillow.

Refer to Seating for switch and system operation.

Heated Seats - Front

Vehicles equipped with front heated seats are equipped with a single-heated seat module to control both front heated seats. The heated seat module is mounted to the bottom of the front passenger seat. The heated seat module does not time out. The system will function with the ignition in RUN, whether the engine is running or not. The heated seat module supplies voltage to the heater mats and regulates seat temperature by monitoring a thermostat located in the cushion heater mat.

The heated seat buttons are part of the Front Controls Interface Module (FCIM). When a heated seat button is pressed, the FCIM (Front Controls Interface Module) sends a command message over Medium Speed Controller Area Network (MS-CAN) to the HVAC module. The HVAC module then momentarily grounds the request circuit to the heated seat module to turn the heated seat ON or OFF. Upon receiving a momentary ground, the heated seat module will decrease one setting (the sequence is high, low, off and high).

When the heated seat module is on it provides a signal back to the HVAC module. The HVAC module then communicates messages back to the FCIM (Front Controls Interface Module) to turn the indicators on. Both indicators illuminate in high, one indicator illuminates in low and neither will be illuminated when off.

The heated seat module does not report DTCs and does not communicate on the CAN (Controller Area 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 OFF and then ON. After the heated seat module has been reset, the module will return to an off state.

The heated seat module request 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. Seats

Normal heat cycle may require several minutes to initially warm the seat. 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 the length of time for the heater mats to reach maximum operating temperature.

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 does not time out. The system will function with the ignition in RUN, whether the engine is running or not. The heated seat module supplies voltage to the heater mats and regulates seat temperature by monitoring a thermostat located in the cushion heater mat.

The heated seat buttons are located in the rear panel of the front floor console. When a heated seat button is pressed, a momentary ground is sent to the heated seat module to turn the heated seat on or off. Pressing the high or low button once turns the heated seat on and pressing the same button a second time turns it off. 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 the heated seat switch is pressed for that high or low mode currently on, sending a second momentary ground signal to the heated seat module or the ignition is set to OFF.

When the heated seat module is on, it provides voltage to the separate indicator circuit at the heated seat button to indicate an on state.

The heated seat module does not report DTCs and does not communicate on the CAN (Controller Area 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 OFF and then ON. After the heated seat module has been reset, the module will return to an off state.

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.

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

Both 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 above 350 rpm, 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) does not time out. The DCSM (Dual Climate Controlled Seat Module) receives voltage from the Battery Junction Box (BJB) on 2 separate circuits. 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 occurs setting a DTC, only the affected seat will be disabled by the module. If the system shuts down due to a DTC fault, 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 system is not equipped with auto-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 what state (high, medium, low or off) it is in back to the HVAC module. The HVAC module 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 MS-CAN (Medium Speed Controller Area Network).

Each driver and front passenger seat 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 foam pad and 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 diagnostic 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 MS-CAN (Medium Speed 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 MS-CAN (Medium Speed Controller Area Network) bus circuits disconnected or shorted to ground. for information concerning MS-CAN (Medium Speed 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 47°C (117°F).

- In the MEDIUM setting, the DCSM (Dual Climate Controlled Seat Module) is set to maintain TED (Thermo-Electric Device) temperature at approximately 55°C (131°F)

- In the HIGH setting, the DCSM (Dual Climate Controlled Seat Module) is set to maintain TED (Thermo-Electric Device) temperature at approximately 62°C (144°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.

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 fan speed and TED (Thermo-Electric Device) supply voltage (duty cycle) in open loop cool mode.

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) 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 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 (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.