Engine Start Button

Components and Component Location

Components (1)

Components (2)

Description and Operation

Description

System Overview

The system provides the following functions:

• Changes the ignition and engine power status using the Start/Stop button.

• Control of external relays for switching the ACC / IGN1 / IGN2 terminals and STARTER, without using a mechanical ignition switch.

• Displays the vehicle status on the display by showing messages.

• Immobilizer function through LF transponder communication between the key and the key holder.

• Redundant architecture for high system reliability.

• Interface with the vehicle Low Speed CAN communication network.

• Interface with the vehicle LIN communication network, depending on platform.

The RKE and SMART KEY functions are not considered part of this push button mechanism. Start system functions are specified in a separate system.

Main system function

• Switching of ACC/IGN1/IGN2 terminals.

• Control of the BAT line of the STARTER relay (high side) based on communication with the EMS ECU.

• Control of the immobilizer function.

• Control of the BES warning function.

Wireless communication

Electrical signals are used to exchange information between the vehicle and the key fob. The push button start system is currently used together with the smart key.

The Smart key function is described separately, so refer to the relevant system contents.

System Block Diagram

System Block Diagram

Integrated Body Control Unit (BCM)

The IBU controls all functions related to:

• Start-stop button (SSB) monitoring

• Immobilizer communication (with the engine control system unit to disable the immobilizer)

• Authentication server (validity of transponder and smart key, optional passive key fob authentication)

• System consistency monitoring

• System diagnostics

• Display message control / warning buzzer control

Limp Home Mode

• If there is no brake input signal (AT specification), the ACC mode must switch to START by pressing the SSM for more than 10 seconds.

• If there is a communication problem between the EMS and CAN (EMS status), the "START" status changes to "ENGINE RUNNING" based on the engine speed input.

• If one of the two SSB input lines is disconnected, electrical power on and off is available by pressing the SSB twice within 10 seconds.

  A buzzer sounds when the button is pressed for the first time.

  The power supply cycle is available, and the buzzer stops when the button is pressed twice within 10 seconds.

Terminal and Starter Relay

The relay is used to switch the ACC/IGN1/IGN2 terminals. The normally open relay is controlled by the smart key unit.

One relay coil is connected to the IBU output terminal.

Electronic Steering Column Lock (ESCL)

The ESCL is required to lock the steering column to prevent unauthorized use of the vehicle.

To achieve the required safety integrity level, the ESCL is controlled and monitored by the IBU.

This redundant architecture ensures that the ESCL motor is powered only during lock/unlock operation and is otherwise disconnected from the battery and ground line to avoid unintended activation while the vehicle is in motion.

Data exchange between the ESCL and IBU is performed through an encrypted serial communication interface.

BES System State Diagram

System States in Learning Mode

In learning mode, the BES can be in 6 different states, depending on the state of the terminals, the ESCL, and the engine:

With regard to the terminals, the system states described in the table above are the same as for a system based on a mechanical ignition switch. The difference from a mechanical ignition switch system is that the BES system allows a transition from [OFF] to [START] without passing through [ACC] and [IGN] positions.

System States in Virgin Mode

The BES system can be set to 5 different states (lock OFF unavailable in virgin mode), depending on the terminal status, ESCL status and engine status:

With regard to the terminals, the system states described in the table above are the same as for a system based on a mechanical ignition switch. The difference from a mechanical ignition switch system is that the BES system allows a transition from [OFF] to [START] without passing through [ACC] and [IGN] positions.