Principles of Operation
PRINCIPLES OF OPERATIONDriver and Passenger Power Seats
The driver and passenger power seat motors are hardwired to the driver or passenger seat control switches. The circuits are normally at ground through the seat control switch. The individual circuit is switched to power when the specific adjustment position is selected.
Power Driver Seat - Memory
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 transmitter. There are 2 memory settings possible. The outside rear view mirror positions and the power adjustable pedals are also stored and recalled with the power driver seat positions.
The driver power seat is controlled by the driver seat module (DSM), if equipped. The DSM does not need to be configured, however the driver seat does need to be calibrated when the DSM is installed or after the driver seat track is installed (if repaired or replaced). 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 power 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 power 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 must be calibrated to the driver seat track for memory seat operation. Once the DSM is calibrated to the seat track, it will only allow movement within the calibrated range.
Seat Calibration
The DSM is calibrated using a diagnostic tool. The calibration procedure automatically powers the driver power seat through its full range of motion and records the full stop positions by monitoring the motor position sensors. Once the full stop positions or range of the seat have been recorded, the DSM will only operate within the calibrated range. Any input attempting to drive the seat beyond the calibrated range will be ignored. This calibration is used for all seat control functions including manual switch control and memory recall positioning. During the seat calibration, the DSM may identify a function that is inoperative, such as a position sensor not changing. If the DSM identifies a concern that has a related diagnostic trouble code (DTC), the DSM will set the related DTC at the end of the validation procedure.
The calibration procedure powers the seat track adjustments to the end of their travel, which is determined by the DSM sensing a change of state in the motor position sensors. If there is a concern with the seat track or motor position sensor that limits the travel, the DSM will interpret the stopping point as the end of travel and store the position. The DSM is not able to determine if the seat has moved to its full travel position. It is only capable of monitoring and storing the amount of travel seen by the position sensor changing states.
Memory Seat
Memory seat positioning can be recalled with the memory switch on the driver door panel or a programmed remote keyless entry transmitter. In either case, the DSM receives a memory recall 1 or 2 command from the driver door module (DDM) over the medium speed controller area network (MS-CAN) communication bus. The memory recall switches are a hardwired input to the DDM. The DDM also receives the remote keyless entry transmitter signals. Once a valid memory recall command is received from the DDM, the DSM moves the driver seat to the position stored in memory by powering the appropriate motors and monitoring the motor position sensors until the position is reached.
This system allows automatic positioning of the driver seat to 2 programmable positions.
- To program position 1, move the driver seat to the desired position using the seat control switch. Depress the SET button. Within 5 seconds, depress button 1.
- To program position 2, repeat the previous procedure using the SET button and button 2.
- To recall position 1, depress button 1. To recall position 2, depress button 2.
A position can only be recalled when the transmission selector is in PARK or NEUTRAL. A position may be programmed at any time.
The DSM communicates diagnostic trouble code (DTC) and other information using the MS-CAN communication bus. It should be noted for diagnostics that because CAN bus communication is more robust and reliable than other methods, it may be possible to have limited module communication with 1 of the CAN bus circuits disconnected or shorted to ground. Refer to Information Bus (Module Communications Network) for additional information concerning MS-CAN bus communication.
Programming Memory Seat Positions
- A power driver seat position can be stored at any time. The driver must move the seat to the desired position using the driver seat switch assembly. The driver must then depress the memory SET switch which activates the memory SET switch light emitting diode (LED) (if equipped). Within 5 seconds (before the LED goes out, if equipped), the driver must select a memory position. Memory 1 is selected by depressing memory switch 1. Memory 2 is selected by depressing memory switch 2.
- If no memory switch input is received within the 5-second time limit, the operation is aborted and the memory SET switch LED is turned off (if equipped). If 1 of the following inputs is received during the 5-second programming limit, the operation is aborted and the memory SET switch LED is turned off (if equipped):
- Power driver seat switch
- Power outside rear view mirror switch
- Memory SET switch
- Power adjustable pedal switch
Recalling a Stored Memory Seat Position
NOTE: A memory recall can be initiated only if the vehicle is in PARK or NEUTRAL gear and the ignition switch is not in START. A memory recall in progress will not be affected by moving the ignition switch to START or by moving the gearshift lever out of PARK or NEUTRAL.
Once the driver has stored the driver seat position, the driver can recall the setting by depressing the corresponding memory switch or by using a programmed remote entry transmitter.
- The driver can recall the desired driver seat position by depressing 1 of the memory recall switches. Depressing memory switch 1 will initiate a recall of the power driver seat position stored in memory 1. Depressing memory switch 2 will initiate a recall of the power driver seat position stored in memory 2.
- A remote transmitter can be used to recall previously set memory positions. The transmitter that has been assigned with personality 1 is capable of recalling memory position 1 only. Similarly, the personality 2 transmitter can recall only memory position 2.
- Memory recall occurs when the UNLOCK switch is depressed on the transmitter. The second depression of the UNLOCK switch, which unlocks passenger doors, does not initiate a memory recall.
- A memory recall in progress does not prohibit the initiation of another memory recall; the most recently requested memory recall will be executed.
Easy Exit/Easy Entry
- The easy exit function moves the seat backwards about 2 inches 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 travel distance to the end of the track or the function has been deactivated. The DSM will also cancel this operation if a valid input command is received, such as the seat control switch or memory recall request.
- 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. Easy entry operation will be cancelled if a valid input command is received by the DSM.
- The easy exit/easy entry feature can be activated or deactivated using a diagnostic tool or via the message center.
Climate Controlled Seat System
Both the driver and front passenger climate controlled seats are independently controlled electronically by the dual climate controlled seat module (dual CCSM) mounted to the bottom of the passenger seat cushion. The climate controlled seat system only operates with the engine running, however, if using a diagnostic tool to command the dual CCSM, diagnostic testing can be carried out with the ignition switch key ON engine OFF (KOEO). The system receives power from battery junction box (BJB) fuse 1.118 (30A) through circuit 1153 (RD/BK) feeding battery voltage into dual CCSM C3265b pins 1 and 24. If power is disconnected from either pin 1 or 24 of dual CCSM C3265b, only 1 seat will be disabled (pin 1 for driver seat, pin 24 for passenger seat), the other will remain operational. Since 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 dual-zone electronic automatic temperature control (EATC) module activate each seat system setting and illuminate LEDs above each switch to indicate the operating mode, 3 LEDs for HIGH, 2 LEDs for MED 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. The climate controlled seat system is not equipped with auto-mode.
Cabin air is drawn through the seat fan motor and distributed to each of the thermo-electric device (TED) modules located in the seat cushion and backrest. The TEDs then heat or cool the air. The air is then directed into the foam pad where it is distributed along the surface of the cushion and backrest of the seat. Once the system is activated, the dual CCSM uses a set of flexible algorithms to control the heating/cooling modes and the fan motor speed dependant on the EATC seat switch settings.
The TED uses a "Peltier" circuit of P-type and N-type semiconductors connected in series using copper electrical conductors. The semiconductors are sandwiched between 2 insulating ceramic plates. When current is applied to the TED, 1 side releases energy as heat, while the opposite side absorbs energy and gets cold. By reversing the current flow, the hot and cold sides reverse.
NOTE: Avoid applying power directly to a TED for testing its operation. Doing so may cause damage to the TED or shorten its usable life.
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 dual CCSM PIDs using the diagnostic tool.
The EATC communicates climate controlled seat commands to the dual CCSM using the medium speed controller area network (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 dual CCSM and EATC for the climate controlled seat switches. 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 dual CCSM. 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 1 of the CAN bus circuits disconnected or shorted to ground. Refer to Information Bus (Module Communications Network) for additional information concerning CAN bus communication.
Heating Characteristics
NOTE: The presence of over-temperature 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 over-temperature condition can result and the DTC(s) will be set.
- The climate controlled seat system draws approximately 9 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 air temperature entering the system.
- There are 3 manual settings based on the LEDs above each seat heat switch button on the EATC. The first setting is HIGH (3 LEDs), the second setting is MED (2 LEDs), the third is LOW (1 LED) then OFF (no LEDs).
- In the LOW setting, the climate controlled seat module is set to maintain TED temperature between 44°C (111°F) and 50°C (122°F).
- In the HIGH setting, the climate controlled seat module is set to maintain TED temperature at 65°C (149°F).
- If the temperature at 1 of the TEDs rises above 90°C (194°F) in the HEAT mode or 70°C (149°F) in the COOL mode for more than 4 seconds, the dual CCSM will record an over-temperature DTC, remove power from the TEDs and go into BLOWER ONLY mode in an attempt to cool down the TEDs. If the TEDs temperature has not dropped to 85°C (185°F) in the HEAT mode or 65°C (140°F) in the COOL mode after 30 seconds, the dual CCSM will shut down and remain off until the ignition is cycled. Also if the dual CCSM detects an over-temperature twice during the same ignition cycle, it will also shut down.
- When heating, the dual CCSM will vary the fan speed and the TED supply voltage in order to reach and maintain the temperature determined by the switch setting.
- Seat heating has a maximum operating duration of 15 minutes.
Cooling Characteristics
- The climate controlled seat system draws approximately 4.5 amps for the first 12 minutes and will operate at 2 amps thereafter.
- In COOL mode, the TED can remove up to 8°C (14°F) from the ambient air temperature entering the system.
- There are 3 manual settings based on the LEDs above each seat cool switch button on the EATC. The first setting is HIGH (3 LEDs), the second setting is MED (2 LEDs), the third is LOW (1 LED) then OFF (no LEDs).
- If the temperature at 1 of the TEDs falls below 18°C (64°F), the climate controlled seat module will shut down the TEDs. If the temperature continues to drop below 12°C (54°F), the climate controlled seat module will shut down the fan motor.
- When cooling, the dual CCSM maintains a constant the fan speed and will vary the TED supply voltage in order to reach and maintain the temperature determined by the switch settings.
- Seat cooling has a maximum operating duration of 30 minutes.
The climate controlled seat system is deactivated by 1 of the following actions:
- Selecting the EATC module setting to manual OFF.
- Turning the vehicle OFF.
Third Row Power-Fold Seat
CAUTION:
- 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.
- 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).
For the third row power-fold seat to operate, a shared ground is supplied by the vehicle security module (VSM) to both of the power-fold seat relays, enabling the seats to then be moved by pressing 1 of the third row power-fold seat switches. The third row power-fold seat operates only when the vehicle is in PARK and the liftgate glass, liftgate door or any entry door must be open.
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 drive cable which is connected to the drive gear assembly. Test M: The Third Row Power Fold Seat Is Inoperative - Left and Right