Front Heated Seats Function - GF91.30-P-0004GWM
Model 463 (except 463.342)
as of model year 2019
Model 463 without code PA9 (Active Multicontour Seat Package)
Model 463 with code PA9 (Active Multicontour Seat Package)
Function requirements, general
- Circuit 15R ON or circuit 15 ON:
The electronic ignition lock control unit sends the status of circuit 15 via the interior CAN to the rear SAM control unit.
Front seat heater, general
The seat heater enables the seat cushions and backrests to be heated in three heating levels. The master control unit for the seat heater function is the rear SAM control unit.
- Function sequence for switching seat heater on and off
- Function sequence for driver seat heater
- Function sequence for front passenger seat heater
- Function sequence for hot-stone (with code PA9 (Active Multicontour Seat Package))
- Function sequence, automatic shutoff
With code PA9 (Active Multicontour Seat Package), the heater pads are energized more than under normal conditions to match the vehicle's interior temperature. This enables faster heating to be achieved. The lower the interior temperature, the faster the heater pads are heated up. The climate control control unit sends the interior temperature value via the interior CAN to the rear SAM control unit. The front seat heater function includes the following subfunctions:
Function sequence for switching seat heater on and off
The seat heater switch in the respective seat climate control switch group and front central locking system switches the seat heater on and off and regulates the heat output (seat heater deactivated in initial condition, all LEDs off):
- Press once: 3 LEDs light up, stage 3 of seat heater activated (100 % heat output)
- Press twice: 2 LEDs light up, stage 2 of seat heater activated (65 % heat output)
- Press three times: 1 LED lights up, stage 1 of seat heater activated (35 % heat output)
- Press four times: All LEDs off, seat heater switched off
If the seat heater is selected again with the same circuit status, heating level 3 is provided with only 90 % of the heat output. The heat output of the respective heating levels can be adjusted ex works via a diagnostic tester.
Function note
The seat heater is switched off automatically at a set time. The timer control is realized by the rear SAM control unit.
- Heating level 3 is activated for 8 min. Then the system automatically switches to heating stage 2.
- Heating stage 2 is activated for 10 min. Then the system automatically switches to heating level 1.
- Heating level 1 is active for 20 minutes. The seat heater is then automatically switched off.
The timer control of the three heating stages can be adjusted in the factory using a diagnostic tester.
Function sequence for driver seat heater
The left front door control unit reads in the status of the left front seat heater switch via the left front door LIN and sends a matching request via the interior CAN to the rear SAM control unit. The rear SAM control unit evaluates this and sends the request to switch on the seat heating over the interior CAN to the driver's seat control unit.
Vehicles without node PA9 (Active Multicontour Seat Package):
The driver seat control unit then actuates the following heater pads directly:
- Left front seat cushion heater pad
- Left front seat backrest heater pad
The driver's seat control unit continuously checks the function of all the components involved in the seat heating and sends the corresponding status over the interior CAN to the rear SAM control unit.
Vehicles with code PA9 (Active Multicontour Seat Package):
The driver's seat control unit forwards the requests over the seat LIN to the driver seat heating control unit.
The driver's seat control unit actuates the following heater pads directly:
- Left front seat cushion side bolster heater pad
- Left front seat backrest side bolster heater pad
The driver seat heater control unit actuates the following heater pads directly:
- Left front seat cushion heater pad
- Left front seat backrest heater pad
To monitor the seat heater, the driver seat control unit and the driver seat heater control unit read in the signals from the corresponding heater pad temperature sensors directly, and evaluates them. The driver seat control unit and the driver seat heater control unit continuously check the functions of all the components involved in the seat heating. The driver seat heater control unit sends the corresponding status via the driver seat-LIN to the driver seat control unit. The driver seat control unit sends the corresponding status via the interior CAN to the rear SAM control unit.
Function feedback
In accordance with the frequency with which the left front seat heater switch is operated, the rear SAM control unit sends the status of the seat heater over the interior CAN, left front door control unit and left front door LIN to the left front seat climate control switch group and front central locking system, which then actuates the LEDs in the left front seat heater switch accordingly.
Function sequence for front passenger seat heater
The right front door control unit reads in the status of the front right seat heater switch over the front right door LIN and sends a corresponding request over the interior CAN to the rear SAM control unit. The rear SAM control unit evaluates this and sends the request to switch on the seat heating over the interior CAN to the front passenger seat control unit.
Vehicles without code PA9 (Active Multicontour Seat Package):
The front passenger seat control unit then actuates the following heater pads directly:
- Right front seat cushion heater pad
- Right front seat backrest heater pad
The front passenger seat control unit continuously checks the function of all the components involved in the seat heating and sends the corresponding status over the interior CAN to the rear SAM control unit.
Vehicles with code PA9 (Active Multicontour Seat Package:
The front passenger seat control unit forwards the requests over the seat LIN to the front passenger seat heating control unit.
The front passenger seat control unit actuates the following heater pads directly:
- Right front seat cushion side bolster heater pad
- Right front seat backrest side bolster heater pad
The front passenger seat heater control unit actuates the following heater pads directly:
- Right front seat cushion heater pad
- Right front seat backrest heater pad
To monitor the seat heater, the front passenger seat control unit and the front passenger seat heater control unit read in the signals from the corresponding heater pad temperature sensors directly, and evaluates them.
The front passenger seat control unit and the front passenger seat heater control unit continuously check the functions of all the components involved in the seat heating. The front passenger seat heater control unit sends the corresponding status via the front passenger seat-LIN to the front passenger seat control unit. The front passenger seat control unit sends the corresponding status via the interior CAN to the rear SAM control unit.
Function feedback
In accordance with the frequency with which the right front seat heater switch is operated, the rear SAM control unit sends the status of the seat heater via the interior CAN, right front door control unit and right front door LIN to the right front seat climate control switch group and the right front central locking system, which then actuates the LEDs in the right front seat heater switch accordingly.
Function sequence for hot-stone (with code PA9 (Active Multicontour Seat Package))
The hot stone function is a comfort function during which the seat heater in the backrest is also switched on in addition to the massage" function. The seat heater remains switched on as long as the massage program is active.
The front left multicontour seat control unit or the front right multicontour seat control unit sends the request to switch on the seat heating over the interior CAN to the rear SAM control unit.
With the hot stone function, only the front seat backrest heater pads are actuated.
The hot stone function can be parameterized using the diagnostic tester.
Function sequence, automatic shutoff
The seat heater is automatically switched off when one of the following events occurs:
- Shut-off in the event of a hardware defect
If a control unit reports the active actuation of a heater pad to the rear SAM control unit, although no request from a seat heater switch is present, the rear SAM control unit switches the seat heater off.
- Deactivation in event of excess temperature of PCBs in respective control unit
- Heating stage 3 can no longer be activated if the PCB temperature is greater than 70 °C.
- Heating stage 3 and heating stage 2 can no longer be activated if the PCB temperature is greater than 80 °C.
- At a printed circuit board temperature of more than 90 °C, the seat heater can no longer be activated.
If the PCB temperature reaches more than 90 °C, a fault message is stored in the fault memory. Manual reactivation requires the printed circuit board temperature to drop to T = 2 °C below the corresponding temperature threshold.
If no circuit board temperature value is present, the interior temperature value is used instead. The climate control control unit sends the interior temperature value via the interior CAN to the rear SAM control unit.
- Shutoff in the event of an error (short circuit, overload or open circuit (line break))
The respective control unit detects a possible short circuit, overload or a line break in the respective heater pad and then switches off the power supply. The fault sources that have been listed can be diagnosed individually for each heater pad using a diagnostic tester.
- Shutoff when the engine starts
When the engine is started (cold start) the seat heater is switched off for 20 seconds. For a hot start, the seat heater is switched off for 3 to 5 seconds. The timer control continues to run, and the LEDs in the respective seat heater switch remain switched on. No undervoltage assessment takes place during startup.
- Switching off by means of energy management
In order to prevent the battery from discharging in all driving cycle phases, the state of charge is continuously evaluated. Depending on the situation, the seat heater is also switched off, if necessary. If the seat heater is switched off, the LEDs in the respective seat heater switch initially remain switched on. If the on-board electrical system returns to the specified voltage again within a period of 3 minutes, the seat heater function is also automatically restarted. If the shutoff takes longer than 3 minutes, the LEDs are also switched off. If the shutoff continues and the function is requested again, the LEDs illuminate for 1.5 seconds and then they go off.
- Switch off in event of voltage drop
If one of the two supply lines (circuit 30 or circuit 30g) of the respective control unit fails, the seat heater is switched off.
- Shutoff after circuit 15R OFF
For circuit 15R OFF and circuit 15C ON, the timer control runs on for another 5 minutes. If circuit 15R is switched on again, the seat heater is also switched on again.
- Shut-off in the event of "Timeout error"
If the request of the rear SAM control unit for actuating the seat heater is discontinued or a "Timeout period" from the electronic ignition lock control unit is recognized, the seat heater is switched off.
- Shutoff at end of diagnosis
The seat heater is switched off after diagnosis is finished.
| Electrical function schematic, seat heater, front | Model 463 (except 463.342) as of model year 2019 with code PA9 (Active Multicontour Seat package) | PE91.30-P-2056-97ZGC | |
| Model 463 (except 463.342) as of model year 2019 except code PA9 (Active Multicontour Seat package) | PE91.30-P-2056-97ZGB | ||
| Overview of system components of comfort heating systems | GF91.30-P-9990GW |