The tables below summarize the input and output signals to the units in the system for the immobilizer. The signal types are divided into directly connected signals, serial communication and controller area network (CAN) communication.

Central electronic module (CEM) (4/56)

Input signals	Output signals
Directly connected:	Directly connected:
Input signals from the switches for the different key positions (I, II, III) in the ignition switch.	Starter motor relay, for activation of starter motor (not applicable to B8444S). Fuel pump (FP) relay for activating the fuel pump (FP).
Via serial communication (LIN):	Via serial communication (LIN):
Antenna ring for communication with the key.	Antenna ring for communication with the key.
Via CAN communication (LS-CAN):	Via CAN communication (LS-CAN):
Phone module (PHM) (16/60) (only vehicles with remote-controlled immobilization).	Driver information module (DIM) for displaying messages. Phone module (PHM) (16/60) (only vehicles with remote-controlled immobilization).
Via CAN communication (HS-CAN):	Via CAN communication (HS-CAN):
Engine control module (ECM) with information about the engine status and for the immobilizer function.	Engine control module (ECM) for communication and checking identity.

Antenna ring (16/65)

Input signals	Output signals
Via serial communication:	Via serial communication:
Central electronic module (CEM) for communication with the key.	Central electronic module (CEM) for communication with the key.

Engine control module (ECM) (4/46)

Input signals	Output signals
Directly connected:	Directly connected:
--	Starter motor relay, for activation of starter motor (applicable to B8444S only).
Via CAN communication (HS-CAN):	Via CAN communication (HS-CAN):
Communication with the central electronic module (CEM) during start attempts.	Information about the engine status Communication with the central electronic module (CEM) during start attempts.

Driver information module (DIM) (5/1)

Input signals	Output signals
Via CAN communication (LS-CAN):	Via Controller Area Network (CAN) communication:
From the central electronic module (CEM) with information about which message must be displayed.	--

Phone module (PHM) (16/60)

Input signals	Output signals
Via Controller Area Network (CAN) communication:	Via Controller Area Network (CAN) communication:
From Central electronic module (CEM) (4/56) with information on remote-controlled immobilization.	To Central electronic module (CEM) (4/56) with information on remote-controlled immobilization.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

System overview: Signals

Use the Manual With the Right Hardware

When to See a Mechanic

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