Description

System Overview. The system provides the following functions:

• Human-machine interface using a single-step button for terminal switching and engine start.
• Control of external relays for switching ACC/IGN1/IGN2 terminals and STARTER, without the use of a mechanical ignition switch.
• Vehicle status indication using LEDs or explicit messages on the display.
• Immobilizer function via low-frequency transponder communication between the fob and the 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 the platform.

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

• 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.

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

• Control of ignition and engine start/stop by sending a signal to the IPM.
• Status display using an LED lamp ON/OFF (amber or reddish-orange).

Indicator ON/OFF Status with Ignition Switch 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	LED is off
2	IG ACC	LED is yellow
3	IGNITION ON (engine off)	LED illuminates in reddish-orange color.
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 system unit to disable the immobilizer),
• "Authentication server" (transponder validity, and in case of Smart Key option, passive FOB authentication),
• "System consistency check",
• "System diagnostics",
• Control of message display / warning buzzer.

The unit acts as the master for the entire system. When SMART KEY is applied, for example, Passive Entry, Passive Lock and Passive Start are integrated for terminal switching operations. It collects vehicle status information from other vehicle modules (vehicle speed, alarm status, driver door open, etc.), reads inputs (for example, SSB, capacitive sensor/lock button, PARK position switch), controls outputs (for example, exterior and interior antennas), and communicates with other devices via the CAN network and LIN interfaces. The SMK is also responsible for diagnosis and learning of the BES system components. The SMK controls functions related to terminal control by activating external relays for ACC, IGN1 and IGN2. This unit is also responsible for control of the STARTER relay. The SMK also controls the SSB illumination and the System Status Indicator, which consists of two LEDs of different colors. Key holder backlight is also controlled by the SMK. The SMK reads inputs (engine start button, vehicle speed, relay contact status), controls outputs (engine relay output drivers), and communicates with other devices via CAN. The internal architecture of the SMK is designed so that terminal control is protected even if one of the two microcontrollers fails, a system inconsistency occurs, or CAN communication is interrupted. If one of the two controllers fails, the remaining controller disables the starter relay. The IGN1 and IGN2 terminal relays must be maintained in the state stored before the failure, and the driver must be able to turn off these IGN terminals by pressing the SSB using the EMERGENCY_STOP press sequence. However, engine restart will be prohibited. The ACC relay state depends on the type of failure. The main functions of the SMK are:

• Control of terminal relays
• Monitoring of vehicle speed received from the sensor or ABS/ESP ECU.
• Control of SSB LEDs (backlight, clamp status).
• Control of the base station located in the SSB via the direct serial port interface.
• Monitoring system consistency to diagnose SMK failure and switch to the appropriate limp-home 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, ACCESSORY, IGNITION and START power modes, by switching the corresponding terminals.
• To start the engine
• To stop the engine

The contact is secured by a microswitch, and backlighting is provided to highlight the button marking when required. Two (2) LED indicators are located in the center of the button to display the system status. Another backlight LED is also built into the SSB to illuminate the Engine Start/Stop symbols.

BES (Engine Start Button) System Status 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 are the same as described in the table above for the system based on a mechanical ignition switch. A distinguishing feature of the BES system, compared with the mechanical ignition switch 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 PRIMARY MODE. The BES system can be set to 5 different states (OFF, LOCKED, unavailable in primary 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 terminals, the system states are the same as described in the table above for the system based on a mechanical ignition switch. A distinguishing feature of the BES system, compared with the mechanical ignition switch system, is that the BES system allows a special transition from [OFF] to [START] without passing through the [ACC] and [IGN] states.