BMW 7 Series: Seat Heating In The Rear Basic Seat

System Circuit Diagram, Rear Seat Heating

Fig. 108: Rear Seat Heating System Circuit Diagram

COMPONENTS DESCRIPTION CHART

1. Seat-heating buttons, driver's side, with function indicator, rear
2. Seat-heating buttons, front-passenger's side, with function indicator, rear

5. Junction box electronics (JB)
6. Seat heating module (SMSH), front passenger, rear
7. Seat heating, seat surface
8. Seat heating, backrest surface
9. Seat heating module (SMSH), driver, rear
10. Seat heating, seat surface
11. Seat heating, backrest surface

KL. 30B - Terminal 30 basic operation
K-CAN2 - Body CAN2
LIN-Bus - Local interconnect network bus

Rear seat heating

The seat heating is available for the left and the right seat and each has a heating circuit. A seat-heating pad is located in each backrest and seat surface. The seat heating can only be activated from "terminal 15 ON".

The seat-heating buttons are integrated under the air vents in the rear center console.

The seat heating function is fully integrated into the junction box electronics.

The junction box electronics evaluate the buttons for the seat heating. To do this the junction box electronics request the current status of the buttons via the LIN bus.

The junction box control unit then transfers the status to the appropriate seat heating module.

The seat heating modules are connected to the junction box electronics via the LIN bus.

NOTE: The seat heating modules are coded to detect the installed position. Different pins are switched to terminal 31, i.e. to ground for coding. The connectors are coded.

The buttons and the seat heating modules are connected to terminal 30B.

The fuses for the buttons and seat heating modules are located in the distribution box in the luggage compartment.

The seat heating can be switched on in three heating stages. The heating stages and their indications are set out in the following table.

SEAT HEATING STAGES

Regulation of the seat heating is controlled via an NTC resistor in the seat-surface seat-heating pad.

Electronic circuitry for indicating operation of the LED and communication via the LIN bus is integrated in each button.

Power reduction of seat heating

The energy management system in the vehicle can activate the seat heating at a reduced power level corresponding to the vehicle's energy balance. The energy management is located in the digital engine-control system.

The digital engine control sends the request to reduce power via the PT-CAN. The central gateway transfers the information to the K-CAN2. The junction box electronics thus know about the request for power reduction.

The junction box electronics send the request for power reduction to the seat heating module.

The reduction stages are:

• Operation of seat heating in Stage 2
• Operation of seat heating in Stage 2 at only 50%
• Seat heating OFF.

NOTE: In the event of a power reduction, the LEDs in the seat-heating switch are not switched off.

During a starting cycle (terminal 50 ON), the seat heating module prevents the seat heating from functioning.

The LED indicator for the activated seat heating remains lit.

Rear-compartment Comfort Seat

The rear-compartment comfort seat is available as part of the luxury rear seating option which is currently only available on the F02.

Fig. 109: Identifying Rear-Compartment Comfort Seat

COMPONENTS DESCRIPTION CHART

1. Memory buttons
2. Seat adjustment function buttons

The rear-compartment comfort seat also has lumbar support. The comfort seat is also known as the multifunction seat.

The seating in the rear-compartment is designed for two persons to increase comfort.

As with its predecessor, the F01/F02 has the seat adjustment switch and memory buttons in separately installed positions.

The seat-adjustment switches are located on the center armrest and are connected via the LIN bus to the seat module. The button for adjusting the lumbar support is located next to the seat adjustment switches.

The memory buttons are integrated into the armrest of the vehicle's rear doors. The memory buttons are connected to the junction box electronics via the LIN bus.

As previously described with the basic seat, the comfort seat also has a method of transferring signals from the seat heating button that differs depending on the equipment installed on the vehicle.

The rear-compartment comfort seat can comes with the ventilation feature. Additionally, there is a "standalone" option for the massage function.

Electric Seat Adjustment for the Rear-compartment Comfort

The comfort seat has the following electric seat adjustment options:

• Seat-inclination adjustment
• Longitudinal seat adjustment SLV (seat distance to front seat)
• Head-restraint height adjustment
• Backrest-inclination adjustment
• Backrest head-inclination adjustment LKV.

The comfort seat has a large seat module that is integrated into the backrest of the seat concerned. All seat adjustment switches are read in by the seat module via the LIN bus. The seat module has sole responsibility for the seat functions. It controls and monitors the function sequences. The seat position of the comfort seat can be adjusted from terminal 30 ON.

NOTE: The seat module is connected via the K-CAN for communicating with other persons in the vehicle electrical system.

The seat module requests the status of the seat adjustment switches via the LIN bus. The seat module activates the adjustment motors in according to the status of the seat adjustment switches. The adjustment motors are activated via the relay in the seat module.

When the seat adjustment switch is released, the seat module cancels activation. The seat module also cancels activation when the adjustment motor is obstructed or when the end position is reached.

An obstructed motor is detected by the current measuring device integrated into the seat module and by failure of the Hall sensor pulses. In this case, the relays are no longer actuated thus shutting down the motors. The seat module also blanks out these adjustment motors when storing the memory position.

Once the motors are unobstructed, they are available to the memory function again.

The seat module stores the malfunctions. In the service workshop, the fault code entry is read out using the diagnostic system.

Fault code memory entries can be:

• Short-circuiting
• Line breaks
• Adjustment motor or Hall sensor is defective.

Fig. 110: Identifying Buttons For Seat Adjustment Functions In F01/F02 Rear-Compartment Comfort Seat (Driver's Side)

COMPONENTS DESCRIPTION CHART

1. Button for lumbar-support adjustment
2. Upper backrest and head restraint height adjustment
3. Reset button
4. Backrest inclination adjustment
5. Longitudinal seat, seat height and seat inclination adjustment

Fig. 111: Identifying Buttons For Seat Functions In F01/F02 Rear-Compartment Comfort Seat (Front- Passenger's Side)

COMPONENTS DESCRIPTION CHART

1. Reset button
2. Upper backrest and head restraint height adjustment
3. Button for lumbar-support adjustment
4. Longitudinal seat, seat height and seat inclination adjustment
5. Backrest inclination adjustment
6. Button for adjusting passenger seat from the rear seat

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