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 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 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 Module Communications Network Testing and Inspection for information concerning MS-CAN 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 transmitter programming, refer to Handles, Locks, Latches and Entry Systems Transmitter.
The DSM is located under the driver seat. To install a new DSM, refer to Driver Seat Module (DSM) Service and Repair. Programmable Module Installation (PMI) must be carried out when installing a new DSM. Refer to Module Configuration [1][2]Initial Inspection and Diagnostic Overview.
This only diagnoses concerns specific to the memory seat. To diagnose a memory exterior mirror concern, refer to Rear View Mirrors Testing and Inspection.
Easy Exit/Easy Entry
The easy entry/easy exit feature is a function of the DSM that moves the driver seat backwards about 50.8 mm (2 in) when the ignition key is removed from the ignition. The DSM receives a key out command over the MS-CAN 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 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 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.
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 Instrumentation, Message Center, and Warning Chimes Description and Operation 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.
NOTE: When installing a new Dual Climate Controlled Seat Module (DCSM), it is necessary to carry out Programmable Module Installation (PMI). Refer to Module Configuration [1][2]Initial Inspection and Diagnostic Overview. Programmable Module Installation (PMI)
The driver and front passenger climate controlled seats are independently controlled by the DCSM. The climate controlled seat system only operates with the engine running, 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 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 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 to function until the DTC resets.
The 4 buttons (identified with seat icons), located on the FCIM, 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 over the 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. The climate controlled seat system can only operate if all 3 modules are communicating correctly on the CAN.
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). 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 located in the seat cushion and backrest. The TEDs 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 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 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 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 Module Communications Network Testing and Inspection for information concerning CAN 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 is set to maintain TED temperature at approximately 46°C (115°F).
- In the MEDIUM setting, the DCSM is set to maintain TED temperature at approximately 60°C (140°F).
- In the HIGH setting, the DCSM is set to maintain TED temperature at approximately 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.
- Engine must be running over 350 rpm and seat heating does not time out.
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.
- When cooling, the DCSM maintains constant speed of the fans and constant TED 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 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 affected seat operation.
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 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 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.