Engine Start Button

Components and Component Location

Component Location

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 for switching the ACC / IGN1 / IGN2 terminals and STARTER, without using a mechanical ignition switch.

• Displays the vehicle status on the display using LEDs or explicit messages.

• Immobilizer function through LF transponder communication between the key and the key 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 mechanism. Start system functions are specified in a separate system.

Main system function

• 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.

Push Button Start System

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 applied, and key authentication and transmission status are satisfied, the BES system continues with steering column lock/unlock, terminal control and engine start.

The driver may release the SSB as soon as 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 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 by pressing and holding the SSB or pressing it 3 times consecutively 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 key is detected and confirmed, the system unlocks the steering column and switches the terminals to IGN. Another press of the SSB is required to start the engine.

For a vehicle equipped with the SMART KEY system, key authentication requires no action by the driver. For emergency start or for a vehicle without SMART KEY, the driver must insert the key into the key 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).

ON/OFF Indicator Status with Ignition Off

ON/OFF Indicator Status by Ignition Key Position

Operation for Each Push Button Start Function

1. 1

   Power supply on / ignition on

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

   • The ignition is turned on by pressing the button with the brake pedal depressed when the shift lever is in P/N with the FOB key.

   

2. 2

   Power OFF / ignition OFF

   • Ignition switching OFF is possible when the vehicle is stopped. (The ignition OFF state is possible regardless of the ATM lever position.)

   • The lever can be shifted to N for parking by pressing the ATM lever unlock button after power is turned off in P.

   

3. 3

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

   • This is a method for forcibly turning off the ignition in case of fuel leakage, vehicle rollover, or an emergency (for example, when the accelerator pedal does not return).

   • The engine is turned off and returns to the ACC state when the button is pressed 3 or more times in succession within 3 seconds for 2 seconds or more while driving. Restart is available within the following 30 seconds regardless of the FOB key and power 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 FOB key. (However, if the shift lever is not in P, ACC ↔ IGN is repeated. Conversion to OFF is not possible.)

   

4. 4

   Brake switch input 0.5-second delay function.

   Starting is possible when the brake pedal is depressed 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 electrical power state.

   • Power OFF: LED OFF

   • ACC power supply status: yellow LED is on

   • Power on: blue LED is on

   • During starting: the previous ON state of the LED is maintained until cranking.

   • Initial state: LED off

Limp Home Mode

• If there is no brake input signal (AT specification), the ACC mode must switch to START by pressing the SSM for more than 10 seconds.

• In case of communication problems between the EMS and CAN (EMS status).

  The state changes from START to ENGINE RUNNING based on the engine speed 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 for the first time.

  The power supply 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 for the immobilizer),

• Authentication server (transponder validity and, in the case of the Smart Key variant, Passive Fob authentication),

• "System consistency check",

• "System diagnostics",

• Control of message display / warning buzzer.

The Smart Key unit controls the entire push button engine start system.

When SMART KEY is applied, such as "Passive Entry," "Passive Lock," and "Passive Authorization," are integrated for terminal switching operations.

It collects vehicle status information from other 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, external and internal antennas), and communicates with other devices via the CAN network as well as single-wire interfaces.

Diagnostics and learning of BES system components are also performed by the SMK.

The SMK controls functions related to terminal control by activating the external relays for ACC, IGN1 and IGN2. This unit is also responsible for controlling the STARTER relay.

The SMK also controls the SSB illumination, as well as the "status indicator system," which consists of 2 LEDs of different colors. The key holder illumination is also controlled by the SMK.

The SMK reads inputs (engine key, vehicle speed, relay contact status), controls outputs (engine relay output drive), 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 network communication is interrupted.

If one of the two controllers fails, the remaining controller must shut off the starter relay. The IGN1 and IGN2 terminal relays must remain 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 sequence. However, restarting the engine will be prohibited. The ACC relay state will depend 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 for diagnosing SMK failure and switching 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 you to:

• 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 necessary.

Three (3) LED colors are located on the outer ring of the switch assembly. They indicate the system status.

They are OFF (white) / ACC (yellow) / ON (green).

BES (Engine Start Button) System State Diagram

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:

Regarding the terminals, the system states described in the table above are the same as those in a system based on a mechanical ignition switch.

One feature that distinguishes the system from one based on a mechanical ignition switch is that the BES system allows a 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, LOCKED, unavailable, in initial mode), depending on the terminal status and engine status:

Regarding the terminals, the system states described in the table above are the same as those in a system based on a mechanical ignition switch.

One feature that distinguishes the system from one based on a mechanical ignition switch is that the BES system allows a transition from [OFF] to [START] without passing through the [ACC] and [IGN] states.