Principles of Operation

Driver and Passenger Power Seats Without Memory

The 10-way 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 state.

The 6-way power seat feature moves the seat in 6 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 power seat feature operates independent of the ignition state.

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 memory driver seat feature allows the driver to program a personalized seat position that can be recalled using the memory switch or a RKE transmitter (if associated). There are 2 memory settings possible.

The DSM does not require calibration to the driver seat track, although soft stops must be set within the seat track physical limits.

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 DTCs and other information using the MS-CAN communication bus. Refer to Module Communications Network for information concerning MS-CAN bus communication.

For information on programming memory positions or recalling a stored memory position, refer to Memory Position Programming .

Easy Entry/Exit Feature

The easy entry/exit feature is a function of the DSM that moves the driver seat backwards about 2 in (50.8 mm) when the ignition key is removed from the ignition switch (without push-button start) or the ignition is turned off (with push-button start). The DSM receives a key in ignition state over the MS-CAN and powers the driver seat rearward. This function will not operate if the seat is less than the 51 mm (2 in) travel distance to the end of the track or the function has been disabled.

The DSM will record the current seat position before powering the seat for an easy exit operation. 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 is received by the DSM.

The easy entry/exit feature can be enabled/disabled in the message center. Refer to the Owner's Literature or Instrumentation, Message Center, and Warning Chimes for information on the message center.

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

DSM Hard Stop/Soft Stop

A hard stop occurs when one of the 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. The seat track axes are forward/rearward, front up/down and rear up/down. To prevent unnecessary stress on the seat, the DSM will set up to 10 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 it will then back up 180 milliseconds 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.

Setting the Soft Stop

NOTE: If a new DSM has been installed, all power driver seat soft stops must be reset. If a new seat track or recline motor has been installed, only reset the soft stops for that component being installed new.

Use the following procedure once a new seat track, recline motor or DSM has been installed.

During the setting procedure, one second after a seat track or seat backrest axis reaches its end of travel in either direction, the DSM will move the motor being used on that particular axis a small amount in the opposite direction of the way the switch is being pressed. Once the motor has moved the seat track or backrest this small amount, the soft stop is set and the switch can be released.

To set the soft stops:

1.

Ignition ON.

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 seat track will then move back a small amount. The horizontal forward soft stop has been set, release the switch button.

4.

Repeat Steps 2 and 3 for all seat track and backrest axes in both directions.

Climate Controlled Seat System

NOTE: Avoid applying voltage directly to a TED for testing its operation. Doing so may cause damage to the TED.

NOTE: When installing a new Front Seat Climate Control Module (SCME), it is necessary to carry out PMI. Refer to Module Configuration .

Both the driver and front passenger climate controlled seats are independently controlled electronically by the Front Seat Climate Control Module (SCME) 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 Front Seat Climate Control Module (SCME), diagnostic testing can be carried out with the ignition ON engine OFF in 15 second durations. The system receives voltage from BJB fuse 67 (40A) supplying battery voltage into the Front Seat Climate Control Module (SCME).

If one of the voltage supply circuits opens, both seats will remain operational because the circuits are connected internally in the Front Seat Climate Control Module (SCME).

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. If the system shuts down due to a DTC fault, cycling the ignition to OFF and then ON again will reset the Front Seat Climate Control Module (SCME) to function until the fault re-occurs.

The 4 climate controlled seat switches (identified with seat icons) on the FCIM activate each seat system setting and illuminate indicators above each switch to indicate the operating mode. There are 3 indicators for HIGH, 2 indicators for MED and 1 indicator for LOW.

Each driver and front passenger seat cushion and backrest is equipped with a TED and blower motor assembly. 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 activated, the Front Seat Climate Control Module (SCME) maintains the heating/cooling modes until deactivated.

The temperature differences between the individual heated and cooled settings is 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 Front Seat Climate Control Module (SCME) PIDs using the scan tool.

When the climate seat buttons (integral to the FCIM) are pressed, the climate controlled seat commands are sent through the I-CAN to the IPC. The IPC sends the request message to the BCM through the HS-CAN. The BCM finally sends the request through the MS-CAN to the Front Seat Climate Control Module (SCME). The climate controlled seats can be commanded on or off using the diagnostic scan tool to verify both module communication on the MS-CAN bus and operation of the Front Seat Climate Control Module (SCME). This method may be useful for isolating a control switch concern. Refer to Module Communications Network for information concerning CAN bus communication.

When the climate control seat buttons are activated on the touchscreen, 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 IPC using the I-CAN. The IPC 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 Front Seat Climate Control Module (SCME) 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 Front Seat Climate Control Module (SCME) and touchscreen 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 Front Seat Climate Control Module (SCME). 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 circuits of a given seat are wired in parallel internally in the Front Seat Climate Control Module (SCME).
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 indicators above each climate controlled seat heat switch button on the FCIM or touchscreen.
In the LOW setting, the Front Seat Climate Control Module (SCME) is set to maintain TED temperature at approximately 46 °C (115 °F).
In the HIGH setting, the Front Seat Climate Control Module (SCME) is set to maintain TED temperature at 65 °C (149 °F).
When heating, the Front Seat Climate Control Module (SCME) 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.

Heating Mode	Initial Temperature	Final Temperature
HIGH	90 °C (194 °F)	65 °C (149 °F)
MED	80 °C (176 °F)	60 °C (140 °F)
LOW	75 °C (167 °F)	46 °C (115 °F)

Cooling Characteristics

In cool mode, the TED circuits of a given seat are wired in series internally in the Front Seat Climate Control Module (SCME).
The climate controlled seat system draws approximately 7 amps.
In cool mode, the TED can remove up to 8 °C (14 °F) from the ambient air temperature entering the system.
The system control settings are based on the indicators above each climate controlled seat cool switch button on the FCIM or touchscreen.
When cooling, the Front Seat Climate Control Module (SCME) maintains constant speed of the fans and constant TED supply voltage (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 buttons on the FCIM or touchscreen
Turning the vehicle OFF

If the temperature at one of the TEDs falls below 5 °C (41 °F), the Front Seat Climate Control Module (SCME) will shut down the TEDs and initiate system recovery mode. If the temperature continues to drop below 2 °C (36 °F), the Front Seat Climate Control Module (SCME) 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 DTC(s) 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 Front Seat Climate Control Module (SCME) 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 Front Seat Climate Control Module (SCME) 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. This scenario 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 Front Seat Climate Control Module (SCME) will disable that seat (fault mode) and remain off until the ignition is cycled. Also, if the Front Seat Climate Control Module (SCME) 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 and that seat will not be operational until the next key cycle.

Heated Seats - Rear

Vehicles equipped with rear heated seats are equipped with a single-heated seat module to control both rear heated seats. The rear heated seat module is located under the front floor console. When the heated seat switch (integral to the RHVAC module) is pressed, a momentary ground signal is sent to the rear heated seat module. Each time the heated seat switch is pressed, it will cycle through the various modes (high, low, and off). When the heated seat feature is active, the rear heated seat module supplies voltage to the heater circuit and also supplies voltage to illuminate the heated seat control switch LEDs (one for low mode, and both for high mode). The seat cushion and backrest heater mats are wired in series. The rear 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 feed output as necessary to maintain the set point temperature. The rear heated seat module will send voltage to the indicator circuit at the heated seat switch to indicate an on state. The rear heated seat module will remain on until the heated seat switch is pressed or the ignition is set to OFF. The rear heated seat module does not time out.

The rear heated seat module does not report DTCs and does not communicate on any network. If a fault is detected the affected seat system will be disabled. The faults detected will be:

a heater feed circuit short to battery, ground or open.
sensor circuit short to battery or open.
heated seat switch stuck closed to ground.

Third Row Power-Fold Seat

NOTE: To prevent possible damage to the third row seat or the safety belts, make sure that the safety belts are not fastened when moving the seat to the load floor position.

NOTE: Make sure that no objects such as books, purses or briefcases are on the floor in front of the third row seats or on the seat cushion before lowering the backrest(s). Failure to follow this instruction may cause incorrect operation of the seat.

For the third row power-fold seat to operate, voltage is supplied by the BCM to the PFSM, enabling the seats to then be moved by pressing the third row seat control buttons. The third row power-fold seats operate only when the vehicle is in PARK and the liftgate glass, liftgate door or any entry door must be open. Sufficient battery voltage is required for PFSM operation. If battery voltage drops below a calibrated threshold, a started seat movement stops. The PFSM does not communicate on any vehicle communication network.

The third row seat control switch contains the seat selector switch buttons. When the third row seat control switch button is momentarily pressed, the affected seat backrest(s) folds down. Pressing the corresponding button again returns the backrest(s) to the original position(s). The PFSM determines which backrest to move by the unique voltage signal received from the third row seat control switch depending on which of the buttons is pressed:

LH seat
RH seat
Both seats

The third row power-fold seat motors transfer movement to a drive gear assembly to raise and lower the seat backrest. The power-fold seat motors rotate a short torque shaft which is connected to the drive gear assembly. The motor assemblies contain Hall-effect sensors that the PFSM uses to monitor motor movement and seat position. The power-fold seat motor and bracket is serviced as an assembly. Refer to Power-Fold Seat Motor .