Principles of Operation

Seats

Principles of Operation

Driver and Passenger Power Seats Without Memory

The driver and front passenger power seat uses a 6-way power seat track and 3 electric motors directly controlled by a seat-mounted seat control switch for horizontal (forward/rearward), front height and rear height adjustment. The driver seat can be equipped with a power recliner mechanism.

Driver Power Seat With Memory

NOTE: A memory recall can be initiated only if the vehicle is in PARK or NEUTRAL gear and the ignition is not in START. A memory recall in progress is not affected by the ignition being in START or by moving the gearshift lever out of PARK or NEUTRAL.

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.

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. This system only diagnoses concerns specific to the memory seat. For information on programming memory positions or recalling a stored memory position, refer to Memory Position Programming Programming and Relearning.

The memory seat is controlled by the Driver Seat Module (DSM). Programmable Module Installation (PMI) must be carried out when installing a new DSM (Driver Seat Module). The DSM (Driver Seat Module) soft stops must be re-set when a new DSM (Driver Seat Module), seat track or recliner motor is installed. Refer to DSM (Driver Seat Module) Hard Stop/Soft Stop.

The DSM (Driver Seat Module) monitors the seat position and motor movement using seat position sensors located at each motor. The DSM (Driver Seat Module) removes power from the motor(s) upon termination of the seat control switch input or if the DSM (Driver Seat Module) does not sense motor movement (determined by monitoring the position sensor).

The DSM (Driver Seat Module) communicates DTC and other information using the MS-CAN (Medium Speed Controller Area Network) communication bus. for additional information concerning MS-CAN (Medium Speed Controller Area Network) bus communication.

Driver Seat Module (DSM) Hard Stop/Soft Stop

A hard stop occurs when the seat track or backrest (recline) axes physically reach the end of travel. 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 (Driver Seat Module). To prevent unnecessary stress on the seat, the DSM (Driver Seat Module) sets 2 soft stops for each moving axis of the seat track and backrest. The DSM (Driver Seat Module) 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, it then backs up 180 milliseconds and establishes the soft stop for that axis in that direction.

Remote Keyless Entry (RKE) Transmitter

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

To associate a remote transmitter to a memory position, refer to Remote Keyless Entry (RKE) Programming in Doors, Hood and Trunk &/or Locks. To diagnose a RKE (Remote Keyless Entry) transmitter concern, refer to Doors, Hood and Trunk &/or Locks.

Easy Entry/Exit Feature

The easy entry/exit feature moves the seat backwards about 50.8 mm (2 in) when the ignition key is removed from the ignition switch. The DSM (Driver Seat Module) receives a key out command over the MS-CAN (Medium Speed Controller Area Network) and powers the driver seat rearward. This function does not operate if the function has been disabled. The DSM (Driver Seat Module) cancels this operation if a valid input command is received, such as the seat control switch or memory recall request.

The DSM (Driver Seat Module) records the current seat position before powering the seat for an easy exit operation. This recorded position is used to return the seat to this position on the easy entry operation. During easy entry operation, when the ignition key is inserted into the ignition switch, the seat is returned to the position previous to the easy exit operation.

The easy entry/exit feature can be disabled and enabled on the message center display menu. or Owner's Literature for instructions for using the message center.

Heated Seats - Front and Rear

Vehicles equipped with front heated seats are equipped with a single-heated seat module to control both front heated seats. 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 functions with the ignition in RUN, whether the engine is running or not. The heated seat module receives separate battery and ignition feeds and a ground source. Upon receiving a command, the heated seat module decreases one setting (the sequence is high, low, off, high). When a heated seat is set to high, both LED indicators on the heated seat control button illuminate. When a heated seat is set to low, only the lower LED indicator illuminates. When a heated seat is set to off, neither LED is illuminated.

The front heated seat switches are part of the Front Controls Interface Module (FCIM). The heated seat system operates independently from the other systems controlled by the FCIM (Front Controls Interface Module). When a button is pressed on the FCIM (Front Controls Interface Module), the MS-CAN (Medium Speed Controller Area Network) communicates the command to the HVAC module. The HVAC module then sends a momentary ground to the heated seat module to turn the heated seat on.

The rear heated seat switches are part of the rear HVAC controls but the heated seat operates independently from the climate control system. When a button on the HVAC controls is pressed, a momentary ground signal is sent to the heated seat module.

Upon receiving a signal, the heated seat module decreases one setting (the sequence is high, low, off, high). When a heated seat is set to high, both LED indicators on the heated seat control button illuminate. When a heated seat is set to low, only the lower LED indicator illuminates. When a heated seat is set to off, neither LED is illuminated.

When the heated seat system is on, the heated seat module then supplies power to the heater mat circuit. The cushion and backrest heater mats of a seat are wired in series and powered by the same output. The heated seat module remains on until the heated seat control button is pressed to cycle the heated seat module off. If the ignition source is removed from the heated seat module, the heated seat module enters an off state and does not return to on until the heated seat control button is once again pressed with the ignition in RUN. Temperature is maintained by the heated seat module, which monitors the temperature sensor in the cushion heater mat and adjusts the current flow to the heater mats.

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.

The heated seat module is designed with an auto-configuration feature for use on other vehicles with a heated seat system using a dual contact (dual throw) heated seat switch. This feature enables additional input circuits not intended for use on this vehicle and causes the heated seats to operate incorrectly. If this occurs, the heated seats both display a symptom of operating only in one mode and illuminating only one indicator. If this condition exists, a reset procedure is required to correctly configure the heated seat module for use. For diagnosis of this condition, GO to Symptom Chart. Symptom Related Diagnostic Procedures

Second Row Power-Fold Seat

NOTE: The Smart Junction Box (SJB) may also be identified as Generic Electronic Module (GEM).

For the second row power-fold seat to operate, voltage is supplied by the SJB (Smart Junction Box) to the power-fold seat relay, enabling the seats to then be moved by pressing the second row power-fold seat switch.

The power-fold seat relay provides voltage on the coil side from the SJB (Smart Junction Box) for 30 minutes when the transmission selector is in PARK, and the liftgate, or liftgate glass, is open. The voltage is 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 motor retracts a cable to release the backrest recliner latches and allows the backrest assist spring to fold the backrest forward onto the seat cushion. The power-fold seat motor continues to retract to release the seat-to floor latches and allows the assist spring and strut dampener to lift and tumble the seat forward to the E-Z entry position for 3rd row seat access. Immediately after the seat is fully released, the power-fold seat motor returns the release cable and latches to a relaxed state, ready for manual latching. To return to a seating position, the seat must be manually latched to the floor and the backrest must be manually latched upright.

Second Row 60/40 Percent E-Z Entry Seats

NOTICE: The backrest must be folded flat (fully downward) before the floor latches can be released. Make sure there are no objects on the seat before lowering the backrest(s). Failure to follow this instruction may cause damage or incorrect operation of the seat.

The 60/40 E-Z entry seats have the following 3 functional positions:

- Backrest fold-flat

- E-Z entry (fold-forward position for third row access)

- Upright

Refer to the Owner's Literature for operating instructions of the E-Z entry seats.

Third Row Power Seats

NOTE: The Smart Junction Box (SJB) may also be identified as the Generic Electronic Module (GEM).

The third row power seat system includes the following components:

- Third row power seat relay

- Power-Fold Seat Module (PFSM)

- Seat control switch

- Power-stow seat motor assembly (contains LH and RH motors and sensors)

- LH and RH power-fold seat motor and sensor assemblies (backrest)

- LH and RH latch assemblies (contains latch motor and latch switch)

The third row power seat relay coil receives voltage from the battery saver relay in the SJB (Smart Junction Box) (courtesy lamp circuit) and ground from the chassis. When energized, the relay switch closes and supplies battery voltage from the Battery Junction Box (BJB) to the PFSM (Power-Fold Seat Module). Sufficient battery voltage is required for PFSM (Power-Fold Seat Module) operation. If battery voltage drops below 8 volts, a started seat movement stops.

When the gear selector lever is in the PARK position and the liftgate is open, the SJB (Smart Junction Box) supplies voltage to the PFSM (Power-Fold Seat Module) enable circuit for 30 minutes. With the ignition OFF, the SJB (Smart Junction Box) disables the battery saver relay after 10 minutes. The system can be re-enabled by opening any door, pressing the unlock button on the RKE (Remote Keyless Entry) transmitter or turning the ignition ON. A short to voltage on the PFSM (Power-Fold Seat Module) enable circuit can result in the third row power seat being operational any time the battery saver relay is energized, regardless of gear selector lever or tailgate position.

The seat control switch contains the seat selector switch button and seat position switch buttons. The PFSM (Power-Fold Seat Module) receives a voltage signal from the seat selector switch for 3 modes:

- LH seat

- RH seat

- BOTH seats

The PFSM (Power-Fold Seat Module) receives voltage signals from the seat position switches for 4 possible seat positions:

- NORMAL

- FOLD

- STOW

- TAILGATE

The power-stow seat motor assemblies rotate the LH or RH seat cushion assemblies together or separately (based on seat[s] selected) and are located at the outboard seat positions. The motor assemblies contain Hall-effect sensors that indicate seat position to the PFSM (Power-Fold Seat Module). The power-stow seat motor assemblies are part of the third row seat pivot tube assembly and are not serviceable separately.

The power-fold motor assemblies rotate the LH or RH seat backrests and are located at the backrest lower outboard positions. The motor assemblies contain Hall-effect sensors that indicate seat backrest position to the PFSM (Power-Fold Seat Module). The LH and RH power-fold motor assemblies are serviceable individually.

The LH and RH latch motors receive voltage from the PFSM (Power-Fold Seat Module). The motors share a common ground supplied by the PFSM (Power-Fold Seat Module). The seat latch motors energize and release the seat latch mechanism(s) when STOW and TAILGATE positions are selected.

The latch switches are normally open and receive approximately 12 volts from the PFSM (Power-Fold Seat Module). The LH and RH latch switches share a common return circuit in series to the PFSM (Power-Fold Seat Module). The PFSM (Power-Fold Seat Module) monitors the latch switch circuits to determine if the seat latches are open or closed. The latch switch is mounted to seat latch mechanism and is not serviceable. A new power seat latch must be installed.

When STOW, FOLD or TAILGATE is selected the backrest folds forward enough to release the spring loaded headrest. If the head restraint is not folded prior to achieving FOLD, STOW or TAILGATE positions, the head restraint becomes an obstruction and prevents the seat from completing the seat movement. When an obstruction is detected during any seat movement, the seat stops, reverses a few inches and then stops again until the obstruction is removed. When the obstruction has been removed the seat control switch must be depressed again to reset the request. The seat goes to the home position (seat folded and latched to the floor) and then continues with the requested seat position. After the seat is repaired or a new system component has been installed, the PFSM (Power-Fold Seat Module) also needs to find the seat's 'home' position before completing a selected seat position.