Principles of Operation

Driver and Passenger Power Seats Without Memory

The 10-way power seat feature operates independently of the ignition position and moves the seat in 10 possible directions:

forward or backward
front and back of the cushion can be moved up and down independently
backrest of the seat can be moved forward and backward
lumbar can be moved in and out

All 10 positions are controlled by a single switch.

The 6-way power seat feature operates independently of the ignition position and moves the seat in 6 possible directions:

forward or backward
front and back of the cushion can be moved up and down independently

The power seat motors are hardwired to the seat control switch. The circuits are normally grounded 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 is executed.

The Driver Seat Module (DSM) controls the driver power memory seat. The DSM is located underneath the driver seat. The memory seat feature allows the driver to program a personalized seat position that can be recalled using the memory SET switch or a Remote Keyless Entry (RKE) transmitter. There are 2 memory settings possible.

For information on programming memory positions or recalling a stored memory position, refer to Memory Position Programming . For additional information on RKE transmitter programming or to diagnose a concern, refer to Handles, Locks, Latches and Entry Systems .

The NEUTRAL position of the driver seat control switch is at a ground state through the seat control switch normally-closed contacts. The driver seat control switch provides voltage to the DSM only when activated. 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. The DSM internally switches the appropriate circuit from ground to voltage to operate the motors.

As the seat is adjusted, the DSM monitors the motor position sensors to record the current seat position. The DSM removes voltage from the motor upon termination of the seat control switch input or if the DSM does not detect movement from the motor while monitoring the position sensor during a memory recall operation.

The DSM communicates DTCs and other information using the MS-CAN. Refer to Module Communications Network for information concerning MS-CAN.

This service information only diagnoses memory seat concerns. To diagnose a memory exterior mirror concern, refer to Rear View Mirrors . To diagnose a memory adjustable pedal concern, refer to Hydraulic Brake Actuation .

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 is executed.

A Remote Keyless Entry (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 pressed on the RKE transmitter if it has been associated with a memory position.

For information on diagnosing an RKE concern or associating an RKE transmitter to a memory position, refer to Handles, Locks, Latches and Entry Systems .

Easy Entry/Easy Exit Feature

The easy entry/exit feature is a function of the DSM that moves the driver seat back approximately 50.8 mm (2 in) (unless seat is already positioned at or near the end of travel) when the ignition key is removed from the ignition switch. The DSM receives a key in ignition status over the MS-CAN and operates the driver seat rearward. The DSM cancels this operation if a valid input command is received from the driver seat control switch, memory SET switch, exterior mirror control switch or if the function has been disabled.

The DSM records the current seat positions before operating the seat for an easy exit operation. This recorded position returns 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 is 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 Instrumentation, Message Center, and Warning Chimes for information on the message center.

Driver Seat Module (DSM) Hard Stop/Soft Stop

The DSM has the ability for soft stops both at the upper and lower limits on all axes of the driver seat. When an axis reaches the hard stop and the switch is held for approximately one second, it then backs up 180 ms and establishes 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.

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 sets soft stop positions, 2 for each moving axis. The DSM uses a preset distance from the hard stop to determine where the soft stop occurs. 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, reset all driver seat track soft stops.

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 immediately press again in the same direction until the seat track stops at the hard stop for that given direction.

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 axes 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.

The driver and passenger heated seat control buttons and indicators are located on the Front Controls Interface Module (FCIM) or touchscreen interface (if equipped). The heated seat system functions independently of the vehicle's climate control system. Each time the heated seat button is pressed, the FCIM sends the request message to the HVAC module which decreases one setting (the sequence is hi, low, OFF, hi, etc.). For vehicles without a touchscreen interface, when a heated seat is set to hi, both LED indicators above that heated seat's control button illuminate. When a heated seat is set to low, only one LED indicator above that switch illuminates. When off, no indicators illuminate.

When activated, the HVAC 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 HVAC module and powered by the output circuit for that seat. The HVAC module monitors inputs from a temperature sensor located in each seat's cushion heater mat, and maintains seat temperature by cycling the heater circuits on/off. The heated seat remains ON until the heated seat switch button is pressed to cycle the HVAC module OFF or the ignition is set to OFF.

If a fault is detected by the HVAC module, the module stops supplying voltage to that individual left or right seat that the fault was detected on until the ignition is turned OFF and then ON.

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 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 pressed while ignition switched voltage is supplied. When a heated seat is set to maximum heat, the high LED indicator on the heated seat switch illuminates. When a heated seat is set to minimum heat, the low LED indicator illuminates.

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. The heated seat module monitors inputs from a temperature sensor, located in each seat's cushion heater mat and maintains seat temperature by cycling the heater circuits on/off. The heated seat module remains ON until the heated seat switch button is pressed to cycle the heated seat module OFF or the ignition switch is set to OFF.

The heated seat module does not report DTCs and does not communicate on any of the CAN. If a fault is detected by the heated seat module, the module stops supplying voltage to that individual left or right seat and switch indicator that the fault was detected on. To reset the heated seat module, cycle the ignition switch OFF and then ON. After the heated seat module has been reset, the module returns to an OFF state.

Climate Controlled Seat System

NOTE: 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 .

Both the driver and front passenger climate controlled seats are independently-controlled electronically by the DCSM mounted to the bottom of the passenger seat cushion. 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 engine off in 15 second durations.

If a fault occurs setting a DTC specific to either climate controlled seat, only the affected seat is disabled by the module. If the system shuts down due to a DTC fault, cycling the ignition to OFF and then ON again resets the DCSM to function until the DTC resets.

Each driver and front passenger seat cushion and backrest is equipped with a Thermo-Electric Device (TED) and blower motor assembly. Voltage is applied to the TED to heat/cool the seat. Applying voltage polarity to the TED in one direction causes the TED 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 activated, the DCSM maintains the heating/cooling modes until deactivated.

The temperature differences between the individual heated and cooled settings are minimal. For example, it is difficult to distinguish between LOW cool and MED cool settings. Measuring seat temperature at different settings is possible by monitoring the DCSM PIDs using the scan tool.

When the climate control seat buttons are activated on the touchscreen interface, the Accessory Protocol Interface Module (APIM) sends the climate controlled seat commands to the FCIM using the I-CAN. The FCIM sends the request message to the IC using the I-CAN. The IC sends the request message to the Body Control Module (BCM) over the HS-CAN. Finally the BCM sends the communicates climate controlled seat commands to the DCSM using the Medium Speed Controller Area Network (MS-CAN). The MS-CAN is connected to the Data Link Connector (DLC) for diagnostic use. No direct connection exists between the DCSM and touchscreen interface for the climate controlled seat buttons. The climate controlled seats can be commanded on or off using the scan tool to verify both module communication on the MS-CAN and operation of the DCSM. This method may be useful for isolating a control switch concern. Refer to Module Communications Network for additional information concerning CAN.

Heating Characteristics

In heat mode, the TED can increase up to 40°C-60°C (104°F-140°F) to the ambient inlet air temperature as it passes over the TED.
The system control settings are based on the 3 indicators above each climate controlled seat heat switch button on the HVAC module.
In the LOW setting, the DCSM is set to maintain TED temperature at approximately 45°C (113°F).
In the HIGH setting, the DCSM is set to maintain TED temperature at 61°C (142°F).
When heating, the DCSM varies the speed of the blowers 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.

Heating Mode	Initial Temperature	Final Temperature
HIGH	80°C (176°F)	61°C (142°F)
MED	70°C (158°F)	55°C (131°F)
LOW	66°C (151°F)	45°C (113°F)

Cooling Characteristics

In cool mode, the TED can decrease up to 8°C (14°F) from the ambient air temperature entering the system.
When cooling, the DCSM maintains constant speed of the blowers and constant TED duty cycle in open loop COOL mode (refer to the following table).

Cooling Mode	TED Voltage	TED Supply Duty Cycle
HIGH	Vbat	100%
MED	Vbat	75%
LOW	Vbat	50%

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

Turning the climate controlled seat system off using the touchscreen interface
Turning the ignition OFF

If the temperature at one of the TEDs falls below 5°C (41°F), the DCSM shuts down the TEDs and initiates system recovery mode. If the temperature continues to drop below 2°C (36°F), the DCSM shuts down the blowers 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 incorrectly operating 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 may 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 records an overtemperature DTC, removes voltage from the TEDs and goes into recovery mode (blower only) for 30 seconds to cool down the TEDs. The same occurs 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 continues 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 continues to cool the TEDs in recovery mode for up to 5 minutes. If the TEDs cool down after 30 seconds, but before 5 minutes (checked at 4 second intervals), the system operates as normal. An overtemperature DTC is still recorded even if the system recovers and is operating normally. This is more likely to occur during extreme cabin temperatures with significant seat back sun load. If the system does not recover within 30 seconds in heat mode or within 5 minutes in cool mode, the DCSM disables that seat (fault mode) and remains off until the ignition is cycled. Also, if the DCSM detects temperature differential fault twice during the same ignition cycle, the DCSM disables the seat. When a fault causes a shutdown, the climate controlled seat indicators turn off and that seat is not operational until the next key cycle.

Remote Start Climate Operation (if equipped)

The customer can select different climate control modes/preferences when the vehicle is started using the remote start feature. This can be accessed through the message center. For additional information on how to set the remote start preferences, refer to the Owner's Literature. When the driver seat and/or passenger seat is set to AUTO mode, the driver/passenger climate controlled seat activates in full heat mode when the outside temperature is less than 0° C (32° F) and full cool mode when outside temperature is greater than 27° C (80° F) whenever the vehicle is started using the remote start feature. No climate control adjustments are recognized during remote start operation. When the ignition is cycled to the ON position after a remote start event, the climate controlled seat switches off.

Second Row Power-Fold Seat

For the second row power-fold seat to operate, voltage is supplied by the BCM to the rear seat release relay, enabling the seats to be moved by pressing the rear power seat release switch. The second row power-fold seat operates only when the vehicle is in PARK and the liftgate door is open.

The rear seat release relay is provided voltage on the coil side from the BCM for 30 minutes after ignition is turned off when the transmission selector is in PARK, and the liftgate door is open. After 30 minutes, the rear seat release relay can be enabled by opening any door, pressing the unlock key on the key fob, pressing any keyless keypad button or turning the ignition ON.

The second row power-fold seat actuators release a locking mechanism allowing the seat backrest to fold down onto the seat cushion.