Principles of Operation
Seats
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 Seats Description and Operation 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 hard-wired 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 MS-CAN 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 bus circuits disconnected or shorted to ground. Refer to Information Bus 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 Doors, Hood and Trunk &/or Locks.
The DSM is located under the driver seat. To install a new DSM, refer to Body Control Systems. Programmable Module Installation (PMI) must be carried out when installing a new DSM. Refer to Information Bus. Programming and Relearning
This only diagnoses concerns specific to the memory seat.
Easy Exit/Easy Entry
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. The DSM receives a key out command over the MS-CAN communication network and powers the driver seat rearward. 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 adjustable pedal 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 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.
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. To prevent unnecessary stress on the seat, 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. 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.
When a new driver seat track with memory or recliner motor, or a DSM 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. 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 Seats Description and Operation 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 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 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. 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. HVAC Module DTC Chart
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. 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.
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. 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. The DCSM 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.
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 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 system is not equipped with auto-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 what state (high, medium, low or off) it is in back to the HVAC module. The HVAC module 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 MS-CAN.
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). 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 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 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 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 MS-CAN 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 bus circuits disconnected or shorted to ground. Refer to Information Bus for information concerning MS-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 47°C (117°F).
- In the MEDIUM setting, the DCSM is set to maintain TED temperature at approximately 55°C (131°F)
- In the HIGH setting, the DCSM is set to maintain TED temperature at approximately 62°C (144°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.
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 fan speed and TED 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 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.