Principles of Operation
Seats
Principles of Operation
Driver and Passenger Power Seats Without Memory
The driver and front passenger power seat motors are hardwired to the seat control switches on each respective seat. The circuits are normally at ground through the seat control switch. Each individual seat track, recliner (if equipped) and lumbar (if equipped) motor circuit is switched to voltage when the 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 memory driver 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 (if associated). There are 2 memory settings possible. The power exterior mirror (if equipped) positions are also stored and recalled with the power driver seat positions.
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 Locks.
The Driver Seat Module (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
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 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 DTC 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 Information Bus for information concerning MS-CAN bus communication.
This only diagnoses concerns specific to the memory driver seat. To diagnose an exterior mirror concern, refer to Mirrors.
Easy Entry/Easy Exit Feature
The easy entry/easy exit feature moves the driver seat backwards about 50.8 mm (2 in) when the ignition key is removed from the ignition switch. 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 driver seat positions before powering the seat for an easy exit operation. This recorded position will be used to return the driver 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.
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.
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.
A 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 a RKE concern or associating a RKE transmitter to a memory position, refer to Locks.
Driver Seat Module (DSM) Hard Stop/Soft Stop
A hard stop occurs when one of the memory seat track axes or backrest recline 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. The seat track axes are forward/rearward, front up/down and rear up/down. The backrest axis is recline forward/backward. To prevent unnecessary stress on the seat and motors, the DSM will set soft stop positions, 2 for each moving axis. 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, the DSM establishes the soft stop for that axis in that direction.
Setting the Soft Stop
NOTE: If a new DSM or driver seat track has been installed, all driver seat track soft stops must be reset.
Use the following procedure once a new seat track or DSM has been installed.
During the setting procedure, if the seat track stops before the end of travel has been reached, the DSM has stopped at a previously set soft stop. To set the new soft stop, release the seat control switch and press again in the same direction until the seat track stops.
1. Turn the ignition 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 horizontal forward soft stop has been set, release the switch button.
4. Repeat Steps 2 and 3 for all seat track axis in both directions.
Heated Seats - Front
WARNING: Never install heated seat parts not intended for use on this vehicle. Parts released for other model years or vehicle lines are not compatible even if they appear visually and physically similar. Installing incorrect parts will result in heated seat system performance outside design specification. Failure to follow this instruction may result in serious personal injury.
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 located under the front passenger seat. The HVAC module includes both driver and passenger heated seat control buttons and indicators. The heated seat system will function independently of the vehicle's climate control system. A momentary ground signal is transmitted to the heated seat module when a heated seat switch button on the HVAC module is depressed and ignition switched voltage is supplied. Upon receiving each control signal to an input circuit, the heated seat module will decrease one setting (the sequence is hi, low, OFF, hi, etc.). When a heated seat is set to hi, both LED indicators above that heated seat's control button will illuminate. When a heated seat is set to low, only one LED indicator above that switch will illuminate. When activated, the heated seat module supplies voltage to the selected seat's heater circuit. Each seat's cushion heater mat and backrest heater mat is connected in a series circuit to the heated seat module and powered by the output circuit for that seat and ground. The heated seat module monitors inputs from a temperature sensor, located in each seat's cushion heater mat and maintains seat temperature by regulating current flow to the heater circuits. The heated seat module will remain ON until the heated seat switch button is depressed to cycle the heated seat module OFF or the ignition switch is set to OFF.
If a fault is detected by the heated seat module, the module will stop supplying voltage to that individual left or right seat and switch indicator, that the fault was detected on. The faults detected will be: a heater supply circuit short to battery, ground or open; sensor circuit short to battery or open; heated seat switch stuck closed to ground. To reset the module, cycle the ignition switch 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 of the CAN.
Heated Seats - Rear
WARNING: Never install heated seat parts not intended for use on this vehicle. Parts released for other model years or vehicle lines are not compatible even if they appear visually and physically similar. Installing incorrect parts will result in heated seat system performance outside design specification. Failure to follow this instruction may result in serious personal injury.
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 located under the rear 60 percent seat. The left and right rear heated seat switches, with indicators, are located in the respective second row door trim panels. A momentary ground signal is transmitted to the heated seat module when a heated seat switch button is depressed and ignition switched voltage is supplied. Upon receiving each control signal to an input circuit, the heated seat module will decrease one setting (the sequence is hi, low, OFF, hi, etc.). When a heated seat is set to hi, both LED indicators on the heated seat switch will illuminate. When a heated seat is set to low, only one LED indicator will illuminate. When activated, the heated seat module supplies voltage to the selected seat's heater circuit. Each seat's cushion heater mat and backrest heater mat is connected in a series circuit to the heated seat module and powered by the output circuit for that seat and ground. The heated seat module monitors inputs from a temperature sensor, located in each seat's cushion heater mat and maintains seat temperature by regulating current flow to the heater circuits. The heated seat module will remain ON until the heated seat switch button is depressed to cycle the heated seat module OFF or the ignition switch is set to OFF.
If a fault is detected by the heated seat module, the module will stop supplying voltage to that individual left or right seat and switch indicator, that the fault was detected on. The faults detected will be: a heater supply circuit short to battery, ground or open; sensor circuit short to battery or open; heated seat switch stuck closed to ground or heated seat switch low and high inputs shorted together. To reset the module, cycle the ignition switch 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 of the CAN.
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 or shorten its usable life.
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 electronically by the DCSM mounted under the front passenger seat. 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 the engine OFF. The system receives voltage on 2 fused circuits from the Battery Junction Box (BJB). If one of the voltage circuits to the DCSM is lost, both seats will remain operational because the circuits are internally connected in the DCSM. If the system shuts down due to a DTC fault, cycling the ignition to off and then on again will reset the DCSM to function until the DTC resets.
Both climate controlled seats operate independently. If a fault occurs setting a DTC specific to either climate controlled seat, only the affected seat will be disabled by the module and the other will remain operational.
The 4 switches (identified with seat icons) on the HVAC module activate each seat system setting and illuminate LEDs above each switch to indicate the operating mode, 3 LEDs for HIGH, 2 LEDs for MEDIUM or 1 LED 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.
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). 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 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 uses a set of flexible algorithms to control the heating/cooling modes and the blower speed dependant on the HVAC seat switch 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 HVAC module communicates climate controlled seat commands to the DCSM using the MS-CAN communication bus. The MS-CAN bus is connected to the Data Link Connector (DLC) for diagnostic use. No direct connection exists between the DCSM and HVAC for the climate controlled seat switches. 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 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.
- The climate controlled seat system draws approximately 24 amperes, with both seats heating, until reaching the set point and then the system operates at a reduced amperage to maintain the climate setting.
- 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 LEDs above each seat heat switch button on the HVAC.
- In the LOW setting, the DCSM is set to maintain TED temperature at approximately 46°C (115°F) (not at seat surface).
- In the HIGH setting, the DCSM is set to maintain TED temperature at 65°C (149°F) (not at seat surface).
- 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.
- Seat heating has a maximum operating duration of 15 minutes.
Cooling Characteristics
- In cool mode, the TED circuits of a given seat are wired in series internally in the DCSM.
- The climate controlled seat system draws approximately 7 amps when in cool mode on high setting.
- In cool mode, the TED can remove up to 8°C (14°F) from the ambient inlet air temperature as it passes over the TED.
- The system control settings are based on the 3 LEDs above each seat cool switch button on the HVAC.
- 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 for cooling mode temperatures.
- Seat cooling has a maximum operating duration of 30 minutes.
The climate controlled seat system is deactivated by one of the following actions:
- Selecting the HVAC module climate control seat switch setting to manual OFF.
- Turning the vehicle OFF.
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 shut down. 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.
Second Row Power-Fold Seat
NOTE: The Smart Junction Box (SJB) may also be identified as the Generic Electronic Module (GEM).
For the second row power-fold seat to operate, voltage is supplied by the SJB to the power-fold seat relay, enabling the seats to then be moved by pressing the second row power-fold seat switch. The second row power-fold seat operates only when the vehicle is in PARK and the liftgate glass or liftgate door is open.
The power-fold seat relay will be provided voltage on the coil side from the SJB for 30 minutes when the transmission selector is in PARK, and the liftgate, or liftgate glass, is open. The voltage will be disabled 30 minutes after turning the vehicle OFF. If the relay is disabled after 30 minutes, it can be enabled by opening any door, pressing the unlock key on the key fob, pressing any keyless keypad button or turning the ignition key.
The second row power-fold seat actuators release a locking mechanism allowing the seat backrest to fold down onto the seat cushion.