Start/Stop Ignition Switch System (With Intelligent Access)

Overview

The push-button ignition system uses the following components to achieve the 4 ignition modes (OFF, ACC, RUN and START):

• BCM
• BPP
• IA key
• RFA module
• Start/stop switch
• TPM module

To achieve any ignition mode other than OFF, the IA key must be present inside the vehicle. The driver does not need to perform any actions on or with the IA key to operate the push-button ignition system. It is sufficient that the IA key is located inside the vehicle when the start/stop switch is pressed. Pressing the start/stop switch causes the RFA module to send out a RF signal to the IA key. The IA key responds by transmitting a RF signal to the TPM module. The TPM module then sends a MS-CAN message to the RFA module that the IA key has responded. Next the RFA module sends a message over the MS-CAN to the BCM indicating that the correct IA key is present. Based on the start/stop switch and BPP switch inputs, the BCM activates the appropriate ignition mode.

Backup Transceiver

If the battery inside the IA key is weak, damaged or if excessive ambient RFI prevents communication between the RFA module and the IA key, the backup transceiver located in the center console storage compartment provides a secondary means for the RFA module to validate the IA key and authorize use of the vehicle. The backup transceiver uses close range RF identification to exchange signals with the IA key, similar to the way an encoded PATS key and transceiver operate. For information on the IA key and backup transceiver, Refer to Section 419-01C .

Push-Button Ignition System Message Center Messages

The message center provides instruction for operating the push-button ignition system. The message center also displays warnings that indicate a potential concern with the system. These messages pertain to the push-button ignition system:

• PRESS BRAKE TO START — Momentarily displays when the start/stop switch is pressed without the brake pedal being applied.
• ACCESSORY POWER ACTIVE — Displays when the vehicle is in ACC mode.
• SHIFT TO PARK — Displays when the start/stop switch is pressed to shut off the engine with the gear selector lever not in PARK.
• RESTART NOW OR KEY IS NEEDED — Displays when the start/stop switch is pressed to shut the engine off and the IA key is not detected in the vehicle.
• NO KEY DETECTED — Displays if the IA key is not detected by the RFA module while attempting to start the vehicle or enter ACC or RUN mode. If this message is observed with the IA key located inside the vehicle, Refer to Section 419-01C .
• STARTING SYSTEM FAULT — Displays if the RFA module receives invalid data from the PCM during PATS authentication. If this message is observed, Refer to Symptom Chart: Passive Anti-Theft System (PATS) in Section 419-01C .

System Operation

System Diagram

Network Message Chart

 Module Network Input Messages — BCM

OFF

To enter OFF mode, press the start/stop button without pressing the brake pedal while the vehicle is in ACC mode, RUN mode or while the engine is running. The IA key does not have to be in the vehicle to achieve OFF mode. However, the IA key must be present to achieve any other ignition mode.

When the engine is running and any one of the vehicle doors is opened and then closed, the RFA module transmits a radio frequency to activate the IA key. If present, the IA key transmits a radio frequency signal to the TPM module. The TPM module sends a message to the RFA module indicating that the IA key is present.

If the IA key is not present, the message center displays NO KEY DETECTED to alert the driver that the IA key is not present.

If the IA key is not present while attempting to enter OFF mode, the message center displays RESTART NOW OR KEY IS NEEDED. The driver then has up to 20 seconds to restart the vehicle without an IA key being present in the vehicle.

ACC

To enter ACC mode, with the correct IA key inside the vehicle, press and release the start/stop switch one time without pressing the brake pedal. Once the BCM receives the message from the RFA module that the correct IA key is present inside the vehicle and the BCM has detected the start/stop switch input without the BPP input, the BCM activates the internal RUN/ACC bus and internal RUN/ACC relay. The BCM also sends the ignition mode message to the other modules over the MS-CAN and the HS-CAN .

Once the ignition has entered ACC mode, the message center displays, PRESS BRAKE TO START and then ACCESSORY POWER ACTIVE.

RUN

To enter RUN mode, with the correct IA key inside the vehicle, press the start/stop switch for a minimum of one second without pressing the brake pedal. Once the BCM receives the message from the RFA module that the correct IA key is present inside the vehicle and the BCM has detected the start/stop switch input without the BPP input, the BCM activates the internal RUN/ACC bus, the internal RUN/START bus, the RUN/ACC relay and the RUN/START relay. The BCM also sends the ignition mode message to the other modules over the MS-CAN and the HS-CAN .

Once the ignition has entered RUN mode, the indicator in the start/stop switch illuminates and the module controlled indicators in the IPC momentarily illuminate to prove they are functioning correctly. For IPC prove out information, Refer to Section 413-01 .

Start

To enter START mode, with the correct IA key inside the vehicle, press and hold the brake pedal, then press and release the start/stop switch. Once the BCM receives the message from the RFA module that the correct key is present inside the vehicle and the BCM has detected the BPP input with the start/stop switch input, the BCM activates the internal RUN/START bus and the RUN/START relay. The BCM also sends the ignition mode message to the other modules over the MS-CAN and the HS-CAN .

The engine can be started from any ignition mode. Once the ignition has entered START mode, the indicator in the start/stop switch illuminates.

Component Description

BCM

The BCM determines the vehicle ignition mode based on the start/stop switch input, the BPP switch input and RFA module messages. The BCM communicates the ignition mode to the other modules over the MS-CAN and the HS-CAN . The BCM monitors the start/stop switch input and the ignition mode outputs. If a fault is detected in the ignition system, DTCs are set in the BCM .

For information about the BCM functions, Refer to Section 419-10 .

Remote Function Actuator (RFA) Module

Refer to Section 419-10 .

Brake Pedal Position (BPP) Switch

The BPP switch (also known as the stoplamp switch) is a dual contact switch. One set of contacts is normally open and receives voltage at all times. The other set of contacts is normally closed and is connected to ground.

When the normally open contacts close, the voltage is sent to the BCM , PCM and RFA module.

When the normally closed contacts open, the ground circuit to the PCM is momentarily interrupted.

Start/Stop Switch

The start/stop switch is a momentary contact switch that is hardwired to the RFA module, BCM , and the PCM. The start/stop switch is connected to both the RFA module and BCM as a backup in case of a switch or circuit failure. In the event of a switch failure or a circuit failure between the switch and one of the modules, the module that receives the start/stop switch request transmits the request over the MS-CAN to the other module to enable ignition system operation.

The start/stop switch also has 2 LEDs , one is used for switch illumination and the other to indicate ignition mode. The ignition mode LED only illuminates when the vehicle is in RUN or START mode, it does not illuminate in ACC mode.