Description and Operation

Description

System Overview. The system provides the following functions:

• Man/machine interface via a single-stage button to switch terminals and start the engine.
• Control of external relays to switch the ACC / IGN1 / IGN2 and STARTER terminals without using a mechanical ignition switch.
• Vehicle status indication by LEDs or text messages on the display.
• Immobilizer function by LF transponder communication between the key fob and the key fob 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.

RKE and SMART KEY functions are not considered part of this engine start button system and are described in a separate system. The main function of the system

• Switching of ACC/IGN1/IGN2 terminals.
• Control of the STARTER relay BAT line (high side) based on communication with the EMS ECU.
• Control of the immobilizer function.
• Control of the BES warning function.

Engine Start Button System. The engine start button system allows the driver to operate the vehicle by simply pressing the button (called SSB) instead of using a conventional mechanical key. If the driver presses the SSB while the brake pedal preconditions are met, key fob authentication and transmission status are completed, the BES system continues with steering column lock/unlock, terminal control and engine start. The driver may release the SSB once this sequence is initiated. After a positive response to the immobilizer check, the system activates the starter and communicates with the EMS to check the engine operating status before cranking. The driver can stop the engine by briefly pressing the SSB if the vehicle is already stationary. An emergency engine stop is possible by pressing and holding the SSB or pressing it 3 consecutive times if the vehicle is in the ENGINE RUNNING state. If the engine start conditions are not met when an SSB press is detected and a valid key fob is authenticated, the system unlocks the steering column and switches the terminals to IGN. Another press of the SSB is required to start the engine. In vehicles equipped with the SMART KEY system, key fob authentication does not require any action from the driver. For a dead battery jump start or in a vehicle without SMART KEY, the driver must insert the key fob into the key fob holder.

• Control of ignition and engine start/stop by sending a signal to the IPM.
• Status indication by the ON/OFF LED lamp (amber or green).

Indicator Light On/Off Status with Ignition Key Off

No.	Indicator lamp	Conditions
1	Indicator lamp is on	Door open, tail lamp on, ACC, IG on
2	Indicator lamp illuminated for 30 seconds → lamp off	Door closed, tail lamp off, ignition off
3	Indicator lamp off	Remote LOCK, passive LOCK
4	Tail lamp dimmer rheostat (illumination lamp)

Indicator ON/OFF Status According to Ignition Switch Position

No.	Ignition conditions	Start button indicator status
1	IG OFF	White LED is on
2	IG ACC	LED is yellow
3	IGNITION ON (engine off)	Green LED is on
4	Cranking	Maintain LED status before start
5	Engine is running	LED is off

Smart Key Unit

The SMK controls all functions related to:

• "Start-stop button (SSB) monitoring",
• "Immobilizer communication" (with the engine control unit for immobilizer unlocking),
• "Authentication server" (transponder validity and, in the case of the Smart Key option, Passive Fob authentication),
• "System consistency check",
• "System diagnostics",
• Control of message display / warning buzzer.

The unit acts as the Master throughout the system. When SMART KEY is used, such as Passive Entry, Passive Lock and Passive Authorization, it is integrated for terminal switching operations. It collects vehicle status information from other modules (vehicle speed, alarm status, driver door open...), reads inputs (such as SSB, capacitive sensor/lock button, PARK switch position), controls outputs (such as external and internal antennas), and communicates with other devices via the CAN network and single-wire interfaces. The SMK also performs diagnostics and monitoring of the BES system components. The SMK controls functions related to "terminal control" by activating external relays for ACC, IGN1 and IGN2. It is also responsible for controlling the STARTER relay. The SMK also controls the SSB illumination, as well as the "system status indicator", which consists of two LEDs of different colors. The key fob holder illumination is also controlled by the SMK. The SMK reads inputs (key fob, vehicle speed, relay contact states), controls outputs (engine relay driver outputs) and communicates with other devices via CAN. The internal architecture of the SMK is designed so that terminal control is maintained even if one of the two microcontrollers fails, a system inconsistency occurs, or CAN network communication is interrupted. If one of the two controllers fails, the remaining controller must disable the starter relay. The IGN1 and IGN2 relay terminals must be maintained in the state that was stored before the failure, and the driver must be able to turn off these IGN terminals by pressing the SSB with the EMERGENCY_STOP press sequence. However, engine restart will not be permitted. The state of the ACC relay depends on the type of failure. The main functions of the SMK are:

• Control of terminal relays
• Monitoring of vehicle speed received from the ABS/ESP sensor or ECU.
• Control of SSB LEDs (backlight, clamp status).
• Control of the base station located in the SSB via direct serial interface.
• System consistency monitoring to diagnose SMK failure and switch to the corresponding fail-safe mode.
• Provision of vehicle speed information
• Start-stop button (SSB) monitoring
• Starter power control

Start/Stop Button (SSB). The single-stage button is used by the driver to operate the vehicle. Pressing this button allows the following:

• To activate the OFF, ACC, IGN and START power modes, switch the corresponding terminals.
• To start the engine
• To stop the engine

The button is secured by a microswitch, and backlighting is provided to highlight the button marking whenever required. Three (3) LED colors are located on the outer ring of the switch assembly. They indicate the system status: OFF (white) / ACC (yellow) / ON (green).

BES (Engine Start Button) System State Table. SYSTEM STATES in LEARNING MODE. In learning mode, the BES system can be set to 6 different states, depending on the terminal status and engine status:

System Status	Terminal status	Engine Status
1. OFF — locked	OFF	Stopped
2. OFF — unlocked	OFF	Stopped
3. ACC	ACC	Stopped
4. IGN	IGN1, IGN2, ACC	Stopped
5. START	IGN1, START	Cranking
6. IGNITION - Engine	IGN1, IGN2, ACC	Run (means "self-sustaining")

Regarding terminals, the system states described in the table above are the same as in a system based on a mechanical ignition lock. One difference from a mechanical ignition switch-based system is that the BES system allows a special transition from [OFF] to [START] without passing through the [ACC] and [IGN] states. SYSTEM STATES IN VIRGIN MODE. The BES system can be set to 5 different states (OFF, LOCK, unavailable in virgin mode), depending on the terminal status and engine status:

System Status	Terminal status	Engine Status
1. OFF - UNLOCKED	OFF	Stopped
2. ACC	ACC	Stopped
3. IGN	IGN1, IGN2, ACC	Stopped
4. Start	IGN1, START with special activation pattern	Cranking
5. IGNITION - Engine	IGN1, IGN2, ACC	Run (means "self-sustaining")

Regarding the terminals, the system states described in the table above are the same as in the system based on a mechanical ignition lock. One difference from the mechanical ignition switch-based system is that the BES system allows a special transition from [OFF] to [START] without passing through the [ACC] and [IGN] states.