Position Determination Of Transmitter Key, Basic Function - GF80.20-P-1009A

MODEL ALL (CAR) 

Overview 

This document contains the following information:

• General 
• Operating principle 

General 

The drive authorization system uses the position determination to determine exactly where the transmitter key is located. Start enable is granted only if the transmitter key is located in the vehicle interior. Start enable must not be granted if the transmitter key is located outside the vehicle. This prevents children in the vehicle from setting the vehicle in motion when the driver has left the vehicle (with the transmitter key), for example.

Vehicles with KEYLESS-GO 

The position of the transmitter key must also be determined accurately outside the vehicle.

Operating principle 

The position search for the transmitter key is activated when the driver requests start enable. An antenna in the vehicle interior transmits radio signals. They are received by the transmitter key. The antenna and the transmitter key then exchange encrypted data. If the transmitter key is not located in the vehicle interior, the starting procedure is not permitted.

Vehicles with KEYLESS-GO 

The position search for the transmitter key is also activated when the following actions are performed:

• Open door
• Open trunk lid or liftgate
• Lock or unlock vehicle via the central locking system

If the transmitter key is not located near the vehicle, it remains locked, for example. Multiple antennae located at the side, front, and back of the vehicle transmit radio signals. The transmitter key receives the signals from the antenna located near it. This antenna and the transmitter key then exchange encrypted data. The position of the transmitter key is verified by evaluating the signal levels of the radio signals and can thus be determined accurately.

If the vehicle is loaded with a large percent by volume of metal, the radio signals emitted by the antennae may be strongly reflected or absorbed. This can cause incorrect detections. In vehicles with KEYLESS-GO, the maximum overlap between the inside and outside areas (measured at the side window) is approx. 10 cm depending on the vehicle contour. This means, the transmitter key is definitely located inside or outside the vehicle above 10 cm. At less than 10 cm (gray zone), the transmitter key position determination may be faulty.

	Function schematics
	Function schematic for detection of transmitter key position	Model 167, 177	PE80.20-P-2503-97A
	Control units
	Electronic ignition lock control unit, basic function		GF80.57-P-9890A
	Components
	Transmitter key, basic function		GF80.35-P-2001A
	KEYLESS-GO antenna, basic function		GF80.61-P-2001A