BMW 7 Series: Seat Heating In The Rear-Compartment Comfort Seat

System Circuit Diagram, Seat Heating

Fig. 115: Rear-Compartment Comfort 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

4. Central gateway module (ZGM)
5. Junction box electronics (JB)
6. Seat module, passenger side, rear (SMBFH)
7. Seat heating, seat surface
8. Seat heating, backrest surface
9. Driver's rear seat module (SMFAH)
10. Seat heating, seat surface
11. Seat heating, backrest surface

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

When the vehicle wakes up, the JBE determine whether a seat module is installed in the vehicle. It sends a corresponding query via the K-CAN2 for this purpose. The central gateway module transfers the signal to the K-CAN.

The ZGM transfers the signal to the K-CAN. This allows the seat module to receive the request, respond to it via the K-CAN and take control of the seat heating function. This means that the button status of the seat heating is evaluated, and the seat heating is activated and monitored.

The JBE request the button status for the seat heating via the LIN bus on a cyclical basis and sends it via the KCAN2.

The ZGM transfers the request for the heating stage to the K-CAN. The seat module evaluates the request for the desired heating stage and activates the seat heating accordingly. The seat heating is a two-circuit heating system.

Function indicator

In order to indicate that the seat heating function has been activated, the seat module sends a request via the KCAN to switch on the LEDs in the button. The request must be transferred on more than one bus system.

The bus systems are, K-CAN (SM > ZGM), K-CAN 2 (ZGM>JB) and LIN (JB>buttons): Back lighting buttons

The FRM sends the status of the terminal 58g ON via the K-CAN2. This is how the junction box electronics receive the status of terminal 58g ON. The JBE send the status of the terminal 58g ON to the seat heating buttons via the LIN bus.

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 ZGM transfers the information to the K-CAN2.

The JBE then receive the request for power reduction and initiates it.

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) or when the seat adjustment switch is operated, the junction box electronics prevent the seat heating from functioning. The LED indicator for the activated seat heating remains lit.

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