Description and Operation

Description

System Overview. The system provides the following functions:

• Changing the ignition and engine power state using the start button.
• Control of external relays for switching the ACC / IGN1 / IGN2 terminals and STARTER, without using a mechanical ignition switch.
• Vehicle status indication on the display using an LED or explicit messages.
• 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 push button start system. They are 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. The push-button start 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 is depressed, and fob authentication and shift position conditions are satisfied, 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 request, the system activates the starter and communicates with the EMS to check the engine operating status for starter release. The driver can stop the engine by briefly pressing the SSB if the vehicle is already stationary. Emergency engine stop is possible by pressing and holding the SSB or pressing it 3 consecutive times if the vehicle ENGINE IS RUNNING. If the engine start conditions are not met when the SSB is pressed 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. In vehicles 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 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)

ON/OFF Indicator Status by Ignition Key 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

   • Power supply state 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 (however, when the shift lever is not in P, the power state continuously changes between ACC and IGN. Conversion to OFF is not possible.)
   • Ignition is turned on by pressing the button with the brake pedal depressed, in P/N position, with the KEY FOB.

   

2. 2
   Power OFF / ignition OFF

   • Ignition can be turned off while the vehicle is stationary. (The ignition OFF state is possible regardless of shift lever position.)
   • The shift lever is moved to N for parking after the power is turned off in P by pressing the shift lever unlock button.

   

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

   • This is the forced ignition shut-off method for the case of fuel leakage after vehicle rollover or in an emergency situation (for example, the accelerator pedal does not return).
   • 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 possible within the following 30 seconds regardless of the FOB key. The power mode changes through OFF → ACC → IGN → OFF by pressing the button without pressing the brake (or with the brake pressed) inside the vehicle with the FOB key. (However, when 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. Starting is possible if the brake pedal is pressed within 0.5 seconds after pressing the start button with the engine off.
5. 5
   The start button status indicator (LED) illuminates depending on the status.

   • Power OFF: LED OFF
   • ACC power supply status: yellow LED is on
   • Power on: blue LED is on
   • During start: Maintains the previous LED status before starting.
   • Initial state: LED off

   

Limp Home Mode

• If there is no brake input signal (AT specification), ACC mode must change to START by pressing the SSM for more than 10 seconds.
• In case of communication problems between EMS and CAN (EMS status), the START status changes to ENGINE RUN based on the RPM input.
• If one of the two SSM 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. The power cycle is available, 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 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 Smart Key Unit controls the entire engine start system from the push button. In SMART KEY applications, the Passive Entry, Passive Lock and Passive Authorization functions are integrated for terminal operation. It collects vehicle status information from other modules (vehicle speed, alarm status, driver door open, etc.), reads inputs (such as SSB, capacitive sensor/lock button, PARK position switch), controls outputs (such as exterior and interior antennas), and exchanges data with other devices via CAN network as well as LIN interfaces. The SMK is also responsible for diagnosis and learning of 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 controlling the STARTER relay. The SMK also controls the SSB illumination and the system status indicator, which consists of 2 LEDs of different colors. Fob holder illumination is also controlled by the SMK. The SMK reads inputs (engine fob, vehicle speed, relay contact status), controls outputs (engine relay drive output), 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 disconnects 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 with the EMERGENCY_STOP press sequence. However, restarting the engine is not 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 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 power modes OFF, ACC, IGN and START, by switching the corresponding terminals.
• To start the engine
• To stop the engine

The contact is protected by a microswitch, and illumination is provided to highlight the button marking when necessary. 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 Status 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 terminals, the system states are described in the table above. They are the same as in a system based on a mechanical ignition switch. One feature that distinguishes it from a mechanical ignition switch is that the BES system allows a direct 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 described in the table above. They are the same as in a system based on a mechanical ignition switch. One feature that distinguishes it from a mechanical ignition switch is that the BES system allows a direct transition from [OFF] to [START] without passing through the [ACC] and [IGN] states.