Principles of Operation
Seats
Principles of Operation
Driver and Passenger Power Seats Without Memory
The 10-way power seat feature operates independently of the ignition position and can move 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 a single switch.
The 6-way power seat feature operates independently of the ignition position and can move 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 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 power memory seat is controlled by the Driver Seat Module (DSM). 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 Programming and Relearning. For additional information on RKE transmitter programming or to diagnose a concern, refer to Handles, Locks, Latches and Entry Systems Transmitter.
The DSM is located underneath the driver seat on the seat track. Carry out Programmable Module Installation (PMI) when installing a new DSM. Refer to Module Configuration Programmable Module Installation (PMI). The DSM does not require calibration to the driver seat track, although soft stops must be set within the seat track physical limits. Refer to Driver Seat Module (DSM) Hard Stop/Soft Stop.
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 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 removes voltage from the motor upon termination of the seat control switch input or if the DSM does not see movement from the motor while monitoring the position sensor.
The DSM communicates DTCs and other information using the MS-CAN communication bus. Because Controller Area Network (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 Module Communications Network Testing and Inspection for information concerning MS-CAN bus communication.
This only diagnoses concerns specific to the memory seat. To diagnose a memory exterior mirror concern, refer to Rear View Mirrors Testing and Inspection. To diagnose a memory adjustable pedal concern, refer to Hydraulic Brake Actuation Testing and Inspection.
Remote Keyless Entry (RKE) Transmitter
An 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. Pressing the unlock switch a second time unlocks the passenger doors but does not initiate a memory recall.
For information on diagnosing an RKE concern or associating an RKE transmitter to a memory position, refer to Handles, Locks, Latches and Entry Systems Testing and Inspection.
Easy Entry/Exit Feature
The easy entry/exit feature is a function of the DSM that moves the driver seat back about 50.8 mm (2 in) when the ignition key is removed from the ignition switch. The DSM receives a key out command 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 Information And Message Center for information on the message center.
Driver Seat Module (DSM) Hard Stop/Soft Stop
A hard stop occurs when one of the memory seat track 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 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. The seat track axes are forward/rearward, front up/down and rear up/down. 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 will occur. When an axis reaches the hard stop and the switch is held for approximately one second in the same direction, 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 press again in the same direction until the seat track stops at the hard stop for that given direction.
1. Turn the ignition key 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.
Climate Controlled Seat System
NOTICE: 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 Programmable Module Installation (PMI).
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 on the seat track. 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. The system receives voltage from Battery Junction Box (BJB) fuse 85 (30A) supplying battery voltage into the DCSM.
If one of the voltage supply circuits opens, both seats remain operational because the circuits are connected internally in the DCSM.
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.
The 4 climate controlled seat switches (identified with seat icons) on the HVAC module activate each seat system setting and illuminate indicators above each switch to indicate the operating mode. Each switch uses 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 Thermo-Electric Device (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 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.
The HVAC module communicates climate controlled seat commands to the DCSM using the Medium Speed Controller Area Network (MS-CAN) bus. The MS-CAN bus is connected to the Data Link Connector (DLC) for diagnostic use. No direct connection exists between the DCSM and HVAC module for the climate controlled seat switches. The climate controlled seats can be commanded on or off using the scan tool to verify both module communication on the MS-CAN bus and operation of the DCSM. This method may be useful for isolating a control switch concern. Refer to Module Communications Network Testing and Inspection 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 DCSM.
- The climate controlled seat system draws approximately 24 amperes, with both seats heating, until reaching the setpoint 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 3 indicators above each climate controlled seat heat switch button on the HVAC module.
- 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. Refer to the following table for heating mode temperatures.
Cooling Characteristics
- In cool mode, the TED circuits of a given seat are wired in series internally in the DCSM.
- 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 3 indicators above each climate controlled seat cool switch button on the HVAC module. The first setting is HIGH (3 indicators), the second setting is MED (2 indicators) and the third is LOW (1 indicator) then OFF (no indicators).
- When cooling, the DCSM maintains constant speed of the blowers and constant TED supply voltage (duty cycle) in COOL mode (refer to the following table).
The climate controlled seat system is deactivated by one of the following actions:
- Selecting the HVAC module setting to manual OFF
- Turning the vehicle 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 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 DTCs 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 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 at anytime 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 sunload. 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, it shuts down.
Remote Start Climate Operation (if equipped)
When the vehicle is started using the remote start feature, 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). No climate control adjustments are recognized during remote start operation. Once the ignition is cycled to the ON position, the climate control system returns to the previous settings (last ignition-ON cycle) and adjustments can be made normally. If the previous setting was off, the climate control turns off. For additional information about remote start operation, refer to Starting System Testing and Inspection or the Owner's Literature.