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 to switch the ACC / IGN1 / IGN2 and STARTER terminals without using a mechanical ignition switch.
• Displays the vehicle status on the display using LEDs or explicit messages.
• 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.

The RKE and SMART KEY functions are not considered part of the engine start/stop button system and are specified in a separate system. 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/Stop Button System. The engine start/stop button 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 transmission status checks are performed, and 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 immobilizer response, the system activates the starter and communicates with the EMS to check the engine running status before cranking. The driver can stop the engine with a short press of the SSB if the vehicle is already stationary. Emergency engine stop is possible with a long press of the SSB or three consecutive presses while the vehicle is in RUNNING ENGINE state. If the engine start conditions are not met when an SSB press is detected and a valid 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. For vehicles equipped with SMART KEY, fob authentication does not require any driver action. For limp-home start or for vehicles 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 indication by the ON/OFF LED lamp (amber or green).

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 on for 30 sec. > 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

Operation for Each Start Button Function

1. 1
   Power supply on / ignition on

   A.

   The power status changes in the sequence OFF > ACC > IGN > OFF by pressing the button, without depressing the brake pedal (or with the brake pedal depressed), inside the vehicle with the key FOB. (When the shift lever is not in P, the power switches continuously between ACC and IGN. Conversion to OFF is not possible.)

   B.	The ignition turns on when the button is pressed with the brake pedal depressed, in the P/N position, with the key FOB.

   

2. 2
   Power OFF / ignition OFF

   A.	Ignition off is possible when the vehicle is stopped. The ignition off state is possible regardless of the ATM lever position.

   B.	Shift lever is moved to N from P after power OFF in P by pressing the ATM lever release button.

   

3. 3
   How to forcibly turn the ignition off and back on while driving

   A.	This is a method for forcibly turning off the ignition in the event of fuel leakage after a vehicle rollover or an emergency situation (e.g., failure of the accelerator pedal to return).

   B.

   The engine is turned off and returns to the ACC state when the button is pressed for 2 seconds or more 3 times in a row within 3 seconds while driving. Restart is available within the following 30 seconds regardless of the key FOB, and the power status changes through OFF > ACC > IGN > OFF by pressing the button, without depressing the brake pedal (or with the brake pedal depressed), inside the vehicle with the key FOB. (However, if the shift lever is not in P, ACC-IGN repeats; conversion to OFF is not possible.)

   

4. 4
   0.5-second delay function for brake switch input. Start is possible if the brake pedal is depressed within 0.5 seconds after pressing the start button with the engine off.
5. 5
   Start button indicator (LED) lights depending on the power supply status.

   A.	Power OFF: LED OFF

   B.	ACC power supply status: yellow LED is on

   C.	Power on: blue LED is on

   D.	During start: maintain the LED status from before start

   E.	Initial state: LED off

   

Limp Home Mode

• If there is no brake input signal (AT specification), the ACC mode must change to START by pressing the SSB for more than 10 seconds.
• In case of a communication problem between EMS and CAN (EMS status), the START state changes to ENGINE RUNNING based on the engine speed input.
• If one of the two SSB input lines is disconnected, power on and off is available by pressing the SSB twice within 10 seconds (SSB LIMP HOME PRESS). A buzzer sounds when the button is pressed the first time. A power cycle is possible, and the buzzer stops when the button is pressed twice within 10 seconds.

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 Smart Key Unit (SMK) controls the entire engine start/stop button system. When SMART KEY applications such as Passive Entry, Passive Lock and Passive Authorization are used, it is integrated for terminal switching operations. It collects vehicle status information from other modules (vehicle speed, alarm status, driver door open...), reads inputs (e.g., SSB, capacitive sensor/lock button, PARK switch position), controls outputs (e.g., exterior and interior antennas), and exchanges data with other devices via the CAN network, as well as single-wire interfaces. The SMK also performs diagnostics and learning of 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 fob holder illumination is also controlled by the SMK. The SMK reads inputs (fob, engine, vehicle speed, relay contact states), controls outputs (engine starter motor relay output) 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, system inconsistency occurs, or CAN network communication is interrupted. If one of the two controllers fails, the remaining controller must disconnect the starter relay. The IGN1 and IGN2 terminal relays must be maintained in their previously stored state until failure, and the driver must be able to switch these IGN terminals off by pressing the SSB with the EMERGENCY_STOP press sequence. However, restarting the engine will be prohibited. 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/Stop Button) System State Table. SYSTEM STATES in LEARNING MODE. In learning mode, the BES system can be in 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 the terminals, the system states described in the table above are the same as in a system based on a mechanical ignition switch. One feature that distinguishes the BES system from a mechanical ignition switch-based system is that the BES system allows a direct transition from [OFF] to [START] without passing through the [ACC] and [IGN] states. SYSTEM STATES IN INITIAL MODE. The BES system can be set to 5 different states (OFF, LOCK, are not available in initial 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 a system based on a mechanical ignition switch. One feature that distinguishes the BES system from a mechanical ignition switch-based system is that the BES system allows a direct transition from [OFF] to [START] without passing through the [ACC] and [IGN] states.