Principles of Operation

HIGH SPEED CONTROLLER AREA NETWORK (HS-CAN) AND MEDIUM SPEED CONTROLLER AREA NETWORK (MS-CAN)

NOTE:
- The high speed controller area network (HS-CAN) circuits that pass through the passenger seat 12 pin electrical connector are part of the main HS-CAN LOOP. If the front passenger seat-to-floor 12 pin electrical connector is disconnected, a NO START condition will result.
- The medium speed controller area network (MS-CAN) circuits that pass through the driver and passenger seat harnesses are part of the main MS-CAN LOOP. If the driver seat-to-floor 57 pin electrical connector is disconnected when equipped with memory seats, various MS-CAN modules will not be able to communicate. If the front passenger seat-to-floor 30 pin electrical connector is disconnected when equipped with climate control seats, various MS-CAN modules will not be able to communicate.

This vehicle utilizes 2 communication systems called HS-CAN and MS-CAN. The memory seat and climate controlled seat communicate over the MS-CAN. When diagnosing the memory seat or climate controlled seat, use a Vehicle Communication Module (VCM) and Integrated Diagnostic System (IDS) software with appropriate hardware, or equivalent scan tool with the latest software update with the capability of communicating over the MS-CAN bus.

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 power when the specific adjustment position is selected.

Power Driver Seat With Memory
The driver power seat is controlled by the driver seat module (DSM), if equipped. 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. There are 2 memory settings possible. The outside rear view mirror positions are also stored and recalled with the power driver seat positions.

The DSM is located underneath the driver seat cushion frame. The DSM does not require calibration to the driver seat track.

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 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 one of the CAN bus circuits disconnected or shorted to ground. Refer to Information Bus (Module Communications Network) for 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 control switch. The driver must then depress the memory SET switch which activates the memory SET switch light emitting diode (LED). Within 5 seconds (before the LED goes out), 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 one 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:-
- Power driver seat control switch
- Memory SET switch

Recalling a Stored Memory Seat Position

NOTE: A memory recall can be initiated only if the vehicle gear selector is in PARK 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.

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 one 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 entry 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 remote entry 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.

Memory positions that have not been programmed will not initiate any motion for the power driver seat or power memory rear view mirrors.

Easy Exit/Easy Entry
The easy exit function moves the seat backwards about 50.8 mm (2 in) when the transmission is in PARK and 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 when the transmission is in PARK and the key is inserted into the ignition lock cylinder. 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 the message center. Refer to the Owner's Literature.

Heated Seats - Front
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 electronic automatic temperature control (EATC) 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 EATC 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 power 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 power to that individual left or right seat and switch indicator, that the fault was detected on. 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. 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 diagnostic trouble codes (DTCs) and does not communicate on any of the controller area networks (CANs).

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. When the heated seat switch is pressed with the ignition switch in RUN, a momentary ground signal is sent to the heated seat module. The heated seat module then supplies power to the heater circuit. The cushion heater mat and seat backrest heater mat are wired in series and powered by the same output. 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 feed output as necessary to maintain the setpoint temperature. The heated seat module also will send voltage to the separate indicator circuit at the heated seat switch to indicate an ON state. The heated seat module will remain on until the heated seat switch is pressed for that circuit that is currently on and receives a second momentary ground signal or the ignition switch is set to OFF.

If a fault is detected by the heated seat module, the module will stop supplying power to that individual left or right seat and switch indicator, that the fault was detected on. 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 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 diagnostic trouble codes (DTCs) and does not communicate on any of the controller area networks (CANs).

Climate Controlled Seat System

NOTE: When installing a new climate controlled seat module (CCSM), it is necessary to carry out programmable module installation (PMI). Refer to Information Bus (Module Communications Network).

Both the driver and front passenger climate controlled seats are independently controlled electronically by the CCSM 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 CCSM, diagnostic testing can be carried out with the ignition switch key on engine off (KOEO). The system receives power on 2 fused circuits from the battery junction box (BJB). If only one of the BJB fuses opens, both seats will remain operational because the power feed circuits are internally connected in the CCSM.

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 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. The climate controlled seat system is not equipped with auto-mode.

Each driver and front passenger seat cushion is equipped with a thermo-electric device (TED) assembly that includes a seat blower (fan motor, serviced as an assembly with the TED). Similarly, each driver and front passenger seat backrest is also equipped with its own TED assembly with blower. 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. 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 CCSM uses a set of flexible algorithms to control the heating/cooling modes and the blower speed dependant on the EATC seat switch settings.

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 CCSM PIDs using the scan tool.

The EATC module communicates climate controlled seat commands to the 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 CCSM and EATC 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 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 one 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







- In heat mode, the TED circuits of a given seat are wired in parallel internally in the CCSM.
- 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 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 medium (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 at approximately 46 °C (115 °F) (not at seat surface).
- In the high setting, the climate controlled seat module is set to maintain TED temperature at 65 °C (149 °F) (not at seat surface).
- When heating, the CCSM 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. Refer to the table for heating mode temperatures.

Cooling Characteristics







- In cool mode, the TED circuits of a given seat are wired in series internally in the CCSM.
- 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 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 medium (2 LEDs) and the third is low (1 LED) then OFF (no LEDs).
- When cooling, the CCSM maintains constant speed of the fans and constant TED supply voltage (duty cycle) in open loop cool mode.

The climate controlled seat system is deactivated by one of the following actions:
- Selecting the EATC module setting to manual OFF.
- Turning the vehicle OFF.

If the temperature at one of the TEDs falls below 5 °C (41 °F), the climate controlled seat module will shut down the TEDs and initiate system recovery mode. If the temperature continues to drop below 2 °C (36 °F), the climate controlled seat module will shut down the affected seat operation.

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 501-10-110 °C (230 °F) in the HEAT mode or 65 °C (149 °F) in the COOL mode for more than 4 seconds, the CCSM will record an overtemperature DTC, remove power 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 30 °C (54 °F) or greater is seen between the backrest and cushion TEDs on either front seat. The CCSM 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 sun-load. If the system does not recover within 30 seconds in HEAT mode or within 5 minutes in COOL mode, the CCSM will disable that seat (fault mode) and remain off until the ignition is cycled. Also, if the CCSM detects an overtemperature or temperature differential fault twice during the same ignition cycle, it will also shut down. When a fault causes a shut-down 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
For the second row power-fold seat to operate, voltage is supplied by the smart power distribution junction box (SPDJB) 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 SPDJB 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.