Engine Start Button

Components and Component Location

Component Location

1. Body Control Module (BCM) 2. Smart Key Module (SMK) 3. Internal Antenna 1 4. Internal Antenna 2 5. Key Fob

6. Start/Stop Button (SSB) 7. Door Handle and Door Antenna 8. Bumper Antenna 9. Rear Door Open Switch

Circuit Diagrams

Wiring Diagram

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 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 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. The push button start system allows the driver to operate the vehicle by simply pressing a button (called the SSB) instead of using a conventional mechanical key. If the driver presses the SSB while the brake pedal is depressed, and smart key authentication and shift position conditions are satisfied, the BES system will continue 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 engagement. 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 by pressing it 3 consecutive times when the vehicle is in the ENGINE RUNNING mode. If the engine start conditions are not met when the SSB is pressed and a valid smart key 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 vehicles equipped with the SMART KEY system, smart key authentication requires no action from the driver. For emergency starting, or in vehicles 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)

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

   • The power supply state changes in the range OFF → ACC → IGN → OFF by pressing the button without depressing the brake (or with the brake depressed) inside the vehicle with the key fob. (However, when the shift lever is not in P, the power state changes continuously between ACC and IGN. Conversion to OFF is not possible.)
   • 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

   • Ignition switch OFF is possible when the vehicle is stopped (ignition OFF state is possible regardless of the shift lever position).
   • 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

   • This is a method of forcibly switching the ignition OFF in the event of fuel leakage when the vehicle overturns, or in an emergency situation (e.g. 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 longer 3 times in a row within 3 seconds while driving. Restart is available within the following 30 seconds regardless of the FOB key. 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 not in P position, 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 pressed 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.

   • Power OFF: LED OFF
   • ACC power supply status: yellow LED is on
   • Power on: blue LED is on
   • During start: maintain the LED status from before start
   • Initial state: LED off

   

Limp Home Mode

• If there is no brake input signal (AT specification), ACC mode shall 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 state changes to ENGINE RUN based on engine speed input.
• If one of the two SSM input lines is disconnected, power ON/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. Power cycling 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 Module (SMK) controls the entire push button engine start system. In vehicles with SMART KEY, the Passive Entry, Passive Lock and Passive Authorization functions are integrated for Terminal Operation switching. 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 position switch), controls outputs (e.g. external and internal antennas), and communicates with other devices via the CAN network and single-line interfaces. The SMK also performs diagnosis and learning of BES system components. The SMK controls functions related to terminal operation by activating external relays for ACC, IGN1 and IGN2. This module is also responsible for controlling the STARTER relay. The SMK also controls the SSB illumination and 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 status), controls outputs (engine relay output driver), and communicates with other devices via CAN. The internal architecture of the SMK is designed so that terminal control is protected even in the event of failure of one of the two microcontrollers, system inconsistency, or interruption of CAN network communication. 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 switch 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 contact is secured by a micro switch and illumination is provided to highlight the button marking when necessary. Three (3) color LEDs 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")

Referring to 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 it from a mechanical ignition switch is that the BES system allows a special 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 and LOCK are not available in initial mode), depending on the terminal state and engine state:

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")

Referring to 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 it from a mechanical ignition switch is that the BES system allows a special transition from [OFF] to [START] without passing through the [ACC] and [IGN] states.