AUTOHOLD [(E)]

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Outline

•  The AUTOHOLD function reduces the load on the driver by maintaining the vehicle in a stopped condition even if the brake pedal is released while the vehicle is stopped.
Caution
•  The AUTOHOLD function is a system which maintains the vehicle in a stopped condition using the DSC brake fluid pressure hold function. Because the function is not for enhancing the tire performance, the vehicle cannot be stopped if the grip limit of the tires is exceeded. Therefore, the function may not be able to hold the vehicle on a steep or slippery road.
Note
•  i-stop operates also during the AUTOHOLD operation. For details on i-stop, refer to the “i-stop control”. (See i-stop CONTROL [SKYACTIV-G (WITHOUT CYLINDER DEACTIVATION (E))].) (See i-stop CONTROL [SKYACTIV-G (WITH CYLINDER DEACTIVATION (E))].) (See i-stop CONTROL [SKYACTIV-D 1.8].)

Functions

•  When the AUTOHOLD switch is on, the DSC HU/CM operates/releases the AUTOHOLD based on the input signal from the ABS wheel-speed sensor and the CAN-related module communication data.

AUTOHOLD display function

•  The AUTOHOLD display function notifies the driver of the system conditions using the AUTOHOLD active indicator light, AUTOHOLD warning beep, and multi-information display.


Structural View

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Hydraulic circuit diagram

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Block diagram

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•  The AUTOHOLD consists of the following parts.

Part name

Functions
DSC HU/CM
(See DSC HU/CM [(E)].)
PCM
(See PCM [SKYACTIV-G (WITH CYLINDER DEACTIVATION (E))].)
(See PCM [SKYACTIV-D 1.8].)
TCM
(See TCM [CW6A-EL].)
(See TCM [ET6A-EL, ET6AX-EL].)
SAS control module
(See SAS CONTROL MODULE [TWO-STEP DEPLOYMENT CONTROL SYSTEM].)
Instrument cluster
(See INSTRUMENT CLUSTER [(E)].)
AUTOHOLD switch
(See AUTOHOLD SWITCH.)
AUTOHOLD active indicator light
(See WARNING/INDICATION/ALARM [DYNAMIC STABILITY CONTROL (DSC) (E)].)
AUTOHOLD warning beep
(See WARNING/INDICATION/ALARM [DYNAMIC STABILITY CONTROL (DSC) (E)].)


Operation


AUTOHOLD control table

Control

Content
AUTOHOLD stand-by control
The AUTOHOLD function enters the stand-by condition when the AUTOHOLD switch is pressed with all of the operation conditions met, and the function becomes operable.
Electric parking brake request control
When any of the electric parking brake operation conditions is met during hold/pressure increase control, the DSC HU/CM operates the electric parking brake.
Hold/pressure increase control
The vehicle is held in the stopped position by maintaining/increasing the brake fluid pressure and operating the brake of each wheel.
Pressure decrease control
Decreases the brake fluid pressure and releases the brakes.
Drive-off control
Determines that the driver is attempting to accelerate the vehicle from a stop during hold/pressure increase control, and releases the brakes.

AUTOHOLD stand-by control
•  When the AUTOHOLD switch is pressed with all of the following conditions met, the AUTOHOLD stand-by indicator light turns on and AUTOHOLD becomes operable.
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―  AUTOHOLD standby indicator light is turned off
―  AUTOHOLD switch is normal
―  Driver’s seat belt is fastened
―  Driver's door is closed
―  DSC system is normal
―  Electric parking brake system is normal
•  When the AUTOHOLD switch is pressed again while the AUTOHOLD is not operating with the AUTOHOLD standby indicator light turned on, the AUTOHOLD indicator light turns off and the function is disabled.
Note
•  If the AUTOHOLD switch is malfunctioning while the AUTOHOLD stand-by indicator light is turned on, the AUTOHOLD indicator light turns off and the function is disabled.
Hold control
•  When all of the following conditions are met, the DSC HU/CM determines that the vehicle is stopped and performs hold control.
―  AUTOHOLD switch is on
―  Wheel speed is 0 km/h {0 mph}
―  Brake fluid pressure is specification or more after depressing brake pedal
―  Accelerator pedal is released
―  Electric parking brake system is normal
―  Electric parking brake is released
―  Electric parking brake switch is not operated
―  Driver seat belt is fastened
―  Driver's door is closed
―  Yaw rate is specification or less (vehicle is stopped)
―  Shift lever is in position other than reverse gear (MTX)
―  Shift lever is in reverse gear and inclination of vehicle rear is 3% or more (MTX)
―  Selector lever is in position other than R (ATX)
―  Selector lever is in R position and inclination of vehicle rear is 6% or more (ATX)
•  When all of the operation conditions are met, the DSC HU/CM controls the traction control solenoid valve, maintains the brake fluid pressure and operates each wheel brake to stops the vehicle. In addition, the AUTOHOLD indicator light turns on.
•  If the driver forcefully depresses the brake pedal and the brake fluid pressure increases, the increased brake fluid is maintained. In addition, the DSC HU/CM continuously maintains hold control for a maximum of 10 min, and operates the electric parking brake.
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Pressure increase control
•  When all of the following conditions are met during AUTOHOLD operation, the DSC HU/CM performs pressure increase control.
―  Wheel speed fluctuation from three wheels or more is detected
―  Brake pedal is released
―  Accelerator pedal is released
Electric parking brake request control
•  When any one of the following conditions is met during hold/pressure increase control, the electric parking brake operates and the electric parking brake indicator light turns on. (See WARNING/INDICATION/ALARM [ELECTRIC PARKING BRAKE (E)].)
―  Ignition is switched OFF
―  Driver seat belt is unfastened
―  Driver's door is opened from closed condition
―  Approx. 10 min or more have elapsed from start of hold/pressure increase control
―  Electric parking brake is normal and vehicle is moving even if pressure increase control is performed
―  Engine is stalled
―  Continuous hold/pressure increase control is not possible
―  Malfunction occurred in AUTOHOLD system
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•  The DSC HU/CM decreases the brake fluid pressure after operating the electric parking brake.
•  When the brake fluid pressure is reduced, the AUTOHOLD active indicator light turns off.
Note
•  For the electric parking brake release conditions, refer to the [ELECTRIC PARKING BRAKE] (electric parking brake release and electric parking brake automatic release). (See ELECTRIC PARKING BRAKE [(E)].)
Pressure decrease control
•  When all of the following conditions are met during hold/pressure increase control, the DSC HU/CM determines that it is not necessary to operate AUTOHOLD and reduces the brake fluid pressure.
MTX
―  Electric parking brake is operated
―  Driver depresses clutch pedal and reverse gear is selected
―  The DSC HU/CM determines that the vehicle is on a flat road or the inclination of the vehicle front is approx. 3% or more based on the longitudinal-G signal from the SAS control module.
ATX
―  Electric parking brake is operated
―  Driver selects R position
―  The DSC HU/CM determines that the vehicle is on a flat road or the inclination of the vehicle front is approx. 6% or more based on the longitudinal-G signal from the SAS control module.
―  Vehicle roll prevention function control request signal from PCM is not sent
•  When the brake fluid pressure is reduced, the AUTOHOLD indicator light turns off.
Drive-off control
•  When any of the following conditions is met with the ignition switched ON (engine on) during hold/pressure increase control, the DSC HU/CM determines that the driver is attempting to accelerate the vehicle from the stop and performs drive-off control.
Driving on a flat road
―  Advance gear or reverse gear (MTX), or D position or R position (ATX) is selected, and accelerator pedal or clutch pedal (MTX) is depressed to specification or more
Vehicle front pitched upward
―  Advance gear (MTX) or D position (ATX) is selected and drive torque required for acceleration occurs by accelerator pedal or clutch pedal (MTX) operation
―  Reverse gear (MTX) or R position (ATX) is selected and accelerator pedal or clutch pedal (MTX) is depressed to specification or more
Vehicle front pitched downward
―  Advance gear (MTX) or D position (ATX) is selected and accelerator pedal or clutch pedal (MTX) is depressed to specification or more
―  Reverse gear (MTX) or R position (ATX) is selected and drive torque required for acceleration occurs by accelerator pedal or clutch pedal (MTX) operation.
•  If the engine torque signal sent from the PCM is the specification or more, or the accelerator pedal or clutch pedal (MTX) is depressed to the specification or more, the DSC HU/CM determines that the vehicle can be accelerated from the stop and decreases the brake fluid pressure. The time under which brake fluid pressure reduction is performed changes depending on the longitudinal-G signal (slope) from the SAS control module.
•  When the brake fluid pressure is reduced, the AUTOHOLD active indicator light turns off.

With i-stop

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Without i-stop

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System malfunctioning

DSC system malfunction
•  If the hold/pressure increase control cannot be performed due to a malfunction in the DSC system, the DSC HU/CM performs the following controls.
AUTOHOLD switch off
―  Inhibits the AUTOHOLD.
AUTOHOLD switch on
During AUTOHOLD non-operation
•  Inhibits the AUTOHOLD.
During hold/pressure increase control
•  The DSC HU/CM sends an electric parking brake request signal immediately. When the electric parking brake operates, the DSC HU/CM inhibits the AUTOHOLD after reducing the maintained brake fluid pressure.
Note
•  If a malfunction in the DSC system occurs and a malfunction in the electric parking brake occurs at the same time during hold/pressure increase control, the brake fluid pressure may be reduced with the electric parking brake not operated. At this time, the DSC HU/CM sends a AUTOHOLD warning beep request signal to the instrument cluster.
During drive-off control and pressure reduction control for certain period of time
•  Inhibits the AUTOHOLD after the brake fluid pressure reduction is completed.
Electric parking brake system malfunction
•  If there is a malfunction in the electric parking brake, the DSC HU/CM performs the following controls.
AUTOHOLD switch off
―  Inhibits the AUTOHOLD.
AUTOHOLD switch on
During AUTOHOLD non-operation
•  Inhibits the AUTOHOLD.
During hold/pressure increase control
―  Inhibits the AUTOHOLD after the drive-off control is completed.
―  The DSC HU/CM sends an AUTOHOLD warning beep request signal to the BCM via CAN communication.
―  When the BCM receives the AUTOHOLD warning beep request signal, the AUTOHOLD warning beep is activated from the notification and warning speaker. (See WARNING/INDICATION/ALARM [DYNAMIC STABILITY CONTROL (DSC) (E)].)

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AUTOHOLD display function operation

•  The AUTOHOLD display function notifies the driver of the system conditions using the AUTOHOLD active indicator light, AUTOHOLD warning beep, and multi-information display.
•  Warning light flashes/message is displayed and beep sound is activated simultaneously for about 5 s. when using AUTOHOLD function or when AUTOHOLD switch is operated. Because a problem with AUTOHOLD function has occurred, AUTOHOLD function does not operate even if AUTOHOLD switch is operated.

Condition

AUTOHOLD active indicator light

Multi-information display
AUTOHOLD is operating
On
—
Indicates when there is a problem with the brake related system while the vehicle is being held in a stop position by the AUTOHOLD function.
On
(Turns off after reducing brake fluid pressure)
Indicates the possibility of the vehicle not being held in the stopped position by the AUTOHOLD function, such as on steep slopes.
On
Indicates when the cancel operation is done without depressing the brake pedal while the vehicle is being held in the stopped position by the AUTOHOLD function.
On
This message is indicated when AUTOHOLD is about to operate and a door is opened or a seat belt is unfastened.
Off