Principles of Operation
Seats
Principles of Operation
Driver (Without Memory) and Passenger Power Seats
The 6-way power seat feature operates independently of the ignition position and moves the seat in 6 possible directions:
- forward or backward
- front and back of the cushion can be moved up and down independently
The 10-way power seat feature operates independently of the ignition position and moves the seat in 10 possible directions:
- forward or backward
- front and back of the cushion can be moved up and down independently
- backrest of the seat can be moved forward and backward
- lumbar can be moved in and out
All 10 positions are controlled by a single switch.
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.
Driver Power Seat With Memory
NOTE: Verify good battery condition before diagnosing the memory seat system. Poor battery condition can 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 Seat Module (DSM) controls the driver power memory seat. The DSM (Driver Seat Module) is located underneath the driver seat. 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 information on RKE (Remote Keyless Entry) transmitter programming or to diagnose a concern, refer to Doors, Hood and trunk &/or Locks.
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 (Driver Seat Module) only when activated. A voltage input causes the DSM (Driver Seat Module) to power the appropriate motor until the input is removed. Ground is the normal state of the motor circuits through the DSM (Driver Seat Module). The DSM (Driver Seat Module) internally switches the appropriate circuit from ground to voltage to operate the motors.
As the seat is adjusted, the DSM (Driver Seat Module) monitors the motor position sensors to record the current seat position. The DSM (Driver Seat Module) removes voltage from the motor upon termination of the seat control switch input or if the DSM (Driver Seat Module) does not detect movement from the motor while monitoring the position sensor during a memory recall operation.
The DSM (Driver Seat Module) communicates DTCs and other information using the MS-CAN (Medium Speed Controller Area Network). Refer to Information Bus for information concerning MS-CAN (Medium Speed Controller Area Network).
This system only diagnoses concerns specific to the memory seat. To diagnose an exterior mirror concern, refer to Mirrors. To diagnose a power adjustable pedal concern, refer to Hydraulic System, Brakes &/or Brake Pedal Assy. To diagnose a power steering column concern, refer to Steering Column.
For information on programming memory positions or recalling a stored memory position, refer to Memory Position Programming Programming and Relearning.
Remote Keyless Entry (RKE) Transmitter
NOTE: A memory recall in progress does not prohibit the initiation of another memory recall; the most recently requested memory recall is executed.
A Remote Keyless Entry (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 (Remote Keyless Entry) transmitter if it has been associated with a memory position.
For information on diagnosing an RKE (Remote Keyless Entry) concern or associating an RKE (Remote Keyless Entry) transmitter to a memory position, refer to Doors, Hood and trunk &/or Locks.
Easy Entry/Easy Exit Feature
The easy entry/exit feature is a function of the DSM (Driver Seat Module) that moves the driver seat back approximately 50.8 mm (2 in) (unless seat is already positioned at or near the end of travel) when the ignition key is removed from the ignition switch. The DSM (Driver Seat Module) receives the key-in ignition status over the MS-CAN (Medium Speed Controller Area Network). The DSM (Driver Seat Module) 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 (Driver Seat Module) records the current seat positions before operating the seat for an easy exit operation. During easy entry operation, the seat is returned to the seat position previous to the easy exit operation. Easy entry operation is cancelled if a valid input command is received by the DSM (Driver Seat Module).
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 Instrument Panel, Gauges and Warning Indicators for information on the message center.
Driver Seat Module (DSM) Hard Stop/Soft Stop
The DSM (Driver Seat Module) 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 (Driver Seat Module) uses this back up strategy to check sensor integrity any time movement has stopped prematurely due to a sensor failure or obstruction.
A hard stop occurs when one of the memory seat track axes or backrest recline 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 seat track axes are forward/rearward, front up/down and rear up/down. The backrest axis is recline forward/backward. To prevent unnecessary stress on the seat and motors, the DSM (Driver Seat Module) sets soft stop positions, 2 for each moving axis. The DSM (Driver Seat Module) uses a preset distance from the hard stop to determine where the soft stop occurs.
Setting the Soft Stop
NOTE: If a new DSM (Driver Seat Module) 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 (Driver Seat Module) has been installed.
During the setting procedure, if the seat track stops before the end of travel has been reached, the DSM (Driver Seat Module) has stopped at a previously set soft stop. To set the new soft stop, release the seat control switch and immediately press again in the same direction until the seat track stops at the hard stop for that given direction.
1. Turn the ignition 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.
Heated Seats - Front
The heated seat system operates independently from the climate control system and is controlled by the heated seat module located underneath the front passenger seat cushion.
On vehicles equipped with a navigation system, the heated seat buttons are part of the Front Controls Interface Module (FCIM) controls. When a heated seat button on the FCIM (Front Controls Interface Module) is pressed, a request message is delivered via MS-CAN (Medium Speed Controller Area Network) communication to the HVAC module. The HVAC module then provides a momentary ground to the heated seat module to command the system on or off.
On vehicles not equipped with a navigation system, the heated seat buttons are part of the HVAC module. When a heated seat button on the HVAC module is pressed, the HVAC module provides a momentary ground to the heated seat module to command the system on or off.
The heated seat module supplies voltage to heater mats located in the seat cushion and backrest to heat the seat. The heated seat module monitors a temperature sensor in each cushion heater mat and regulates the seat temperature. The heated seat module is designed to remain on, heating the seat and maintaining temperature until switched off.
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 monitors the heater output and thermistor circuits for fault detection but does not report DTCs and is not connected to the communication bus circuits. If an open circuit or short to ground occurs, the output is disabled to the heater mats and the heated seat indicators turn off. When a fault is detected, the heated seat module only disables the affected seat and the other seat may continue to operate normally. The heated seat cannot be operated until the system is repaired and the ignition is cycled OFF and ON to reset the heated seat module from the detected fault.
The HVAC module monitors the control circuits to the heated seat module and will set a DTC if a circuit fault is detected. Refer to the HVAC Module DTC Chart. Seats
The heated seat module is used on 2 different heated seat systems, front heated seat only or front and rear heated seats. These systems use 2 different on/off switches, a single momentary switch and a dual momentary switch. A new heated seat module is programmed to function for a single momentary switch system and is designed with an auto-configuration feature. If a new module is installed in a dual momentary switch system, the auto-configuration feature sets the operating characteristics of the module the first time a heated seat button is pressed. Once the module is configured for a dual momentary switch system it does not function correctly in a single momentary switch system unless the module is reset. Refer to Heated Seat Module Reset .
If the module has been auto-configured for a dual momentary switch system and is then installed in a single momentary switch system, the front heated seats displays both 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.
Heated Seats - Rear, Crew Cab
Rear heated seats are controlled by the heated seat module located behind the rear 60 percent seat backrest and a dual momentary switch attached to each rear door panel. When the heated seat switch is pressed, a momentary ground signal is sent to the heated seat module. The heated seat module then supplies voltage to the heater circuit. The seat cushion and backrest heater mats are wired in series and supplied voltage by the same output. The heated seat module monitors inputs from a temperature sensor, located in each cushion heater mat and maintains seat temperature by cycling output voltage to the heater grids as necessary to maintain the set point temperature. The heated seat module supplies voltage to the appropriate indicator circuit in the heated seat switch. The heated seat module does not time out and remains on until switched off or ignition is OFF.
The heated seat module does not report DTCs and does not communicate on any network. If a fault is detected, the affected seat system is disabled. The faults detected are:
- a heater feed circuit short to battery, ground or open.
- sensor circuit short to battery or open.
- heated seat switch stuck closed to ground.
- heated seat switch low and high inputs shorted together.
To reset the module, cycle the ignition OFF and then ON. After the heated seat module has been reset, the module returns to an off state.
A new heated seat module must be configured after installation for correct operation. Heated seat module configuration occurs automatically when the low heat mode button is pressed on either rear heated seat switch. Until the module is correctly configured, the heated seats operates incorrectly from the high heat mode button on either heated seat switch by following a sequence of high, low and off with each button press. After the low heat mode button is pressed on either heated seat switch, the module correctly configures and the system operates correctly.
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 (Thermo-Electric Device).
NOTE: When installing a new Dual Climate Controlled Seat Module (DCSM), it is necessary to carry out Programmable Module Installation (PMI). Programming and Relearning
Both the driver and front passenger climate controlled seats are independently controlled electronically by the DCSM (Dual Climate Controlled Seat Module) mounted to the bottom of the passenger seat cushion. The climate controlled seat system only operates with the engine running. However, if a scan tool is used to command the DCSM (Dual Climate Controlled Seat Module), diagnostic testing can be carried out with the ignition ON engine OFF in 15 second durations.
If one of the voltage supply circuits opens, both seats will remain operational because the circuits are connected internally in the DCSM (Dual Climate Controlled Seat Module).
If a fault occurs and sets 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 (Dual Climate Controlled Seat Module) to function until the DTC sets again.
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 to the TED (Thermo-Electric Device) in one direction causes it to heat. Applying voltage polarity in the opposite direction causes the TED (Thermo-Electric Device) to cool. Cabin air is drawn through the blower and distributed to each of the TED (Thermo-Electric Device) modules located in the seat cushion and backrest. The TEDs (Thermo-Electric Devices) 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 (Dual Climate Controlled Seat Module) 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 DCSM (Dual Climate Controlled Seat Module) PIDs using the scan tool.
The HVAC module communicates climate controlled seat commands to the DCSM (Dual Climate Controlled Seat Module) using the Medium Speed Controller Area Network (MS-CAN) bus. The MS-CAN (Medium Speed Controller Area Network) bus is connected to the Data Link Connector (DLC) for diagnostic use. No direct connection exists between the DCSM (Dual Climate Controlled Seat Module) 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 (Medium Speed Controller Area Network) bus and operation of the DCSM (Dual Climate Controlled Seat Module). This method can be useful for isolating a control switch concern. for information concerning CAN (Controller Area Network) bus communication.
Heating Characteristics
- In heat mode, the TED (Thermo-Electric Device) can add up to 40-60°C (72-108°F) to the ambient inlet air temperature as it passes over the TED (Thermo-Electric Device).
- The system control settings are based on the 3 indicators above each climate controlled seat heat switch button on the HVAC module.
- In the LOW setting, the DCSM (Dual Climate Controlled Seat Module) is set to maintain TED (Thermo-Electric Device) temperature at approximately 46°C (115°F) at the TED (Thermo-Electric Device).
- In the HIGH setting, the DCSM (Dual Climate Controlled Seat Module) is set to maintain TED (Thermo-Electric Device) temperature at 69°C (156°F) at the TED (Thermo-Electric Device).
- When heating, the DCSM (Dual Climate Controlled Seat Module) varies the speed of the blowers and the TED (Thermo-Electric Device) 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 (temperatures are at the TED (Thermo-Electric Device) ).
Cooling Characteristics
- In cool mode, the TED (Thermo-Electric Device) 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 (Dual Climate Controlled Seat Module) maintains constant speed of the blowers and constant TED (Thermo-Electric Device) supply voltage (duty cycle) in open loop 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 (Thermo-Electric Devices) falls below 5°C (41°F), the DCSM (Dual Climate Controlled Seat Module) will shut down the TEDs (Thermo-Electric Devices) and initiate system recovery mode. If the temperature continues to drop below 2°C (36°F), the DCSM (Dual Climate Controlled Seat Module) will shut 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 are set.
If the temperature at one of the TEDs (Thermo-Electric Devices) 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 (Dual Climate Controlled Seat Module) records an overtemperature DTC, remove voltage from the TEDs (Thermo-Electric Devices) and go into recovery mode (blower only) for 30 seconds to cool down the TEDs (Thermo-Electric Devices). The same occurs if a temperature difference of 60°C (108°F) or greater is seen between the backrest and cushion TEDs (Thermo-Electric Devices) on either front seat. The DCSM (Dual Climate Controlled Seat Module) continues to monitor the TEDs (Thermo-Electric Devices) while in recovery mode. If the temperature of the TEDs (Thermo-Electric Devices) 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 (Thermo-Electric Devices) in recovery mode for up to 5 minutes. If the TEDs (Thermo-Electric Devices) cool down at anytime after 30 seconds, but before 5 minutes (checked at 4-second intervals), the system operates as normal. An overtemperature DTC still is 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 (Dual Climate Controlled Seat Module) disables that seat (fault mode) and remain off until the ignition is cycled. Also, if the DCSM (Dual Climate Controlled Seat Module) detects temperature differential fault twice during the same ignition cycle, it shutdowns. When a fault causes a shutdown, the climate controlled seat indicators turns off and that seat is not operational until the next key cycle.
Remote Start Climate Operation (If Equipped With Heated Or Climate Controlled Seats)
The customer can select different climate control modes/preferences when the vehicle is started using the remote start feature. This can be accessed through the message center. For information on how to set the remote start preferences, refer to the Owner's Literature. When the driver seat and/or passenger seat is set to AUTO mode, the driver/passenger heated/climate controlled seat activates in full heat mode when the outside temperature is less than 0°C (32°F) and full cool mode (climate controlled seats only) when outside temperature is greater than 27° (80°F) any time the vehicle is started using the remote start feature. No heated/climate controlled seat adjustments are recognized during remote start operation. When the ignition is cycled to the ON position after a remote start event, the heated/climate controlled seat switches off.