Auto Idle Stop System Description

For locations of each component on vehicle, refer to Component Location Index

Overview

System Description

The auto idle stop system is a system that stops and restarts the engine automatically to help maximize fuel economy depending on enviromental and vehicle operating conditions.The system can help reduce fuel consumption, idling noise and any emissions. Conditions such as driver's operation, vehicle state and environment determine if the vehicle can enter auto idle stop.

Basic System Operations

During auto idle stop, the auto idle stop indicator (green) indicator turns on in the gauge control module.
The auto idle stop system is executed when the certain conditions are met. Refer to the Available Conditions for Auto Idle Stop.
If one of the conditions are met, the engine restarts automatically. However, there are conditions that will prohibit the engine to start automatically.Refer to Engine Restart Conditions After Auto Idle Stop and Disable Conditions for the Engine Restart After Auto Idle Stop.
The driver can cancel the auto idle stop system from operating with the auto idle stop off switch.
When the system is off, the auto idle stop off indicator in the gauge control module turns on.
If the auto idle stop can not be executed because of a system malfunction, the auto idle stop system indicator (amber) in the gauge control module blinks.

Auto Idle Stop Indicator

Courtesy of HONDA, U.S.A., INC.

System Determination Pattern

After the vehicle is turned to the ON mode, the system is activated and starts a constant monitor of various conditions.The system then determines if a auto idle stop or an engine restart (after the engine has stopped) can be executed.

Auto idle stop at full stop (vehicle speed is 0 mph (0 km/h))

Courtesy of HONDA, U.S.A., INC.

Auto Idle Stop Control Signal

The PCM monitors signals from control units, sensors and switches to determine if the vehicle can execute/continue an auto idle stop or if it can restart the engine.When the PCM determines that the auto idle stop can executed, it stops the fuel injection and stops the engine.When it determines an engine restart, it operates the starter and resumes fuel injection to start the engine.If the PCM receives a malfunction signal from a control unit or the conditions are not met, the auto idle stop is not executed.

Transmitting and Received Signals to/from PCM

Target unit, sensor and switch	Transmitting Signal	Received Signal	Remarks
Related control units	System malfunction signal* 1	-	See Detailed Information of the Control or Communication Signal
Idle stop off switch	Auto idle stop cancellation signal	-	-
SPORT mode switch	Sport mode ON/OFF signal	-	-
Hood latch switch	Hood open/close signal	-	-
Driver's seat belt switch	Seat belt latched/unlatched signal	-	-
CVT speed sensor	Vehicle speed/vehicle speed record information	-	-
EPS control unit	Steering torque signal Steering torque signal Steering angle information	-	-
Transmission range switch	Shift position information	-	The signal is sent to the TCM. The TCM sends the determination of the auto idle stop system to the PCM based on the signal.
Transmission fluid temperature sensor	Transmission warm-up information	-	The signal is sent to the TCM. The TCM sends the determination of the auto idle stop system to the PCM based on the signal. -
Auxiliary transmission fluid pump	-	During engine stop: pump operation command signal When engine restarting: pump stop command signal	Auxiliary transmission fluid pump is controlled by the TCM.
Brake pedal position switch	Brake pedal on/off signal	-	-
VSA modulator-control unit	Hydraulic control operating information Vehicle speed information Master cylinder pressure information* 1 Starting Assist Brake Function information Automatic brake hold system operating information Electric parking brake system operation information	Starting Assist Brake request signal	See Detail Information of the Control or Communication Signal
Electric brake booster	Electric brake booster system information	-	-
SRS unit	Vehicle inclination angle information	-	-
Accelerator pedal module (APP sensor)	Accelerator pedal on/off signal	-	-
Engine coolant temperature (ECT) sensor	Engine warm-up information	-	-
Climate control unit	Auto idle stop permission signal by the climate control system	-	See Detail Information of the Control or Communication Signal
Starter	-	Starter operating command signal* 1	-
12 volt battery sensor	12 volt battery status information Internal resistance value Battery fluid temperature Current value Voltage value	-	See Detail Information of the Control or Communication Signal

*1: See detailed information*2: With the Adaptive Cruise Control (ACC) with the Low Speed Follow (LSF)

Target unit, sensor and switch	Transmitting Signal	Received Signal	Remarks
DC-DC converter	Unit quality information	-	See Detail Information of the Control or Communication Signal
Gauge control module	-	Indicator lamps on/off signal or blink signal Auto idle stop message indication signal When the auto idle stop cannot be executed or the engine cannot be restarted: Idle stop message indication is indicated (See Detail Information of the Control or Communication Signal)	During auto idle stop: Auto idle stop indicator (green) is turned on Engine oil pressure warning indicator goes off Charging system indicator goes off When the auto idle stop system off switch is on: Auto idle stop indicator (amber) is turned on When there is a failure of the auto idle stop system: Auto idle stop indicator (amber) blinks
ACC with LSF* 2	ACC/LSF operating information	-	See Detail Information of the Control or Communication Signal
Injector	-	Fuel injection stop/injection command signal	-
Alternator	-	Alternator operating command	-

*1: See detailed information*2: With the Adaptive Cruise Control (ACC) with the Low Speed Follow (LSF)

Detail Information of the Control or Communication Signal

System Malfunction Signal

If a malfunction in the following systems that are related to the auto idle stop have occured, a warning indicator is turned on or blinks, and the auto idle stop is prohibited. A warning indicator is displayed on the gauge control module (multi-information display), and informs the malfunction to the driver.

System malfunction indications for prohibiting the auto idle stop

System	Warning indicator	Remarks
Auto idle stop system	Courtesy of HONDA, U.S.A., INC.	Possible cause: DC-DC converter 12 volt battery sensor Alternator Climate control unit Brake system (master cylinder pressure information)
Charging system	Courtesy of HONDA, U.S.A., INC.	-
Starter system	Courtesy of HONDA, U.S.A., INC.HONDA, U.S.A., INC. Courtesy of HONDA, U.S.A., INC.HONDA, U.S.A., INC. NOTE: There are some kinds of indications which are different by applicable area.	-

System	Warning indicator	Remarks
PGM-FI system	Courtesy of HONDA, U.S.A., INC.	Even if this indicator is displayed, the auto idle stop system may be enabled according to the contents of malfunction.
CVT control system	Courtesy of HONDA, U.S.A., INC.	All segments blink.
EPS control system	Courtesy of HONDA, U.S.A., INC.	-
VSA system (ABS)	Courtesy of HONDA, U.S.A., INC.	Even if this indicator is displayed, the auto idle stop system may be enabled according to the contents of malfunction.
VSA system	Courtesy of HONDA, U.S.A., INC.	Even if this indicator is displayed, the auto idle stop system may be enabled according to the contents of malfunction.
Brake system	Courtesy of HONDA, U.S.A., INC.HONDA, U.S.A., INC. Courtesy of HONDA, U.S.A., INC.HONDA, U.S.A., INC. (Red) NOTE: There are some kinds of indications which are different by applicable area.	Even if this indicator is displayed, the auto idle stop system may be enabled according to the contents of malfunction.
Electric brake booster system	Courtesy of HONDA, U.S.A., INC.HONDA, U.S.A., INC. Courtesy of HONDA, U.S.A., INC.HONDA, U.S.A., INC. (Red) NOTE: There are some kinds of indications which are different by applicable area.	Electric brake booster system malfunction

System	Warning indicator	Remarks
Automatic brake hold system	Courtesy of HONDA, U.S.A., INC.HONDA, U.S.A., INC. Courtesy of HONDA, U.S.A., INC.HONDA, U.S.A., INC. (Amber) NOTE: There are some kinds of indications which are different by applicable area.	Even if this indicator is displayed, the auto idle stop system may be enabled according to the contents of malfunction.
SRS system	Courtesy of HONDA, U.S.A., INC.	Even if this indicator is displayed, the auto idle stop system may be enabled according to the type of malfunction.

Master Cylinder Fluid Pressure Information (lack of brake pedal force)

The master cylinder fluid pressure information is transmitted to the PCM via the VSA modulator-control unit.If the brake pedal force by the driver is insufficient, and if the master cylinder fluid pressure is less than specified value, the auto idle stop is prohibited. In this case, a message is displayed in the multi-information to inform the driver.

Courtesy of HONDA, U.S.A., INC.

Idle Stop Permission Signal from the Climate Control System

To maintain cabin comfort, the climate control unit transmits the auto idle stop activate, prohibit or engine restart judgment to the PCM based on sensors and switches. When a engine restart request is received from during idle stop, the auto idle stop indicator is turned off and the engine restarts. If the climate control unit malfunctions, the malfunction information is sent to the PCM, and the auto idle stop system warning indicator (amber) blinks.

Transmitting and received signals to/from climate control unit

Target unit, sensor and switch	Transmitting Signal	Received Signal
ECON switch	ECON ON/OFF mode selection signal	-
Engine coolant temperature (ECT) sensor	Engine warm-up information	-
Windshield defrost button/switch	Windshield defrost on/off signal	-
Temperature and fan control button/switch (climate control unit)	Cabin temperature and air volume setting information	-
Outside air temperature sensor	Outside air temperature information	-
Evaporator temperature sensor/in-car temperature sensor	In-car temperature information in the cabin	-
Humidity sensor	Humidity information in the cabin	-
Sunlight sensor	Sunlight information	-

Target unit, sensor and switch	Transmitting Signal	Received Signal
PCM	-	Auto idle stop implementation/prohibition determination information within the climate control system.

Starter Operating Command Signal

The PCM counts the number of times that the start operates and if it exceeds a specified number, prohibits auto idle stop operation. In this case, the indicator on the gauge control module (amber) blinks.The starter and the starter cut relay (in the relay circuit board) operation number are memorized in the PCM.

Indicator for the starter operation over times

Courtesy of HONDA, U.S.A., INC.

12 Volt Battery Status Information

The PCM receives the 12 volt battery status signal and determines the state of quality and its amount of deterioration. When a malfunction is detected, the auto idle stop operation is prohibited and a message is displayed in the multi-information display to alert the driver (when the battery is deteriorated).

Courtesy of HONDA, U.S.A., INC.

MID (auto idle stop system problem)

If there is a malfunction in the auto idle stop system and related systems, the auto idle stop indicator will turn on with a message on the multi-information display.

Courtesy of HONDA, U.S.A., INC.

MID (auto idle stop unavailable)

If the auto idle stop system and related systems are normal but auto idle stop operation is prohibited by the system, the following message will be displayed in the multi-information display.

Courtesy of HONDA, U.S.A., INC.

MID (auto engine idle stop: engine will restart soon)

The following message with be displayed right before the engine is restarted by the system when the auto idle stop system is in operation.

Courtesy of HONDA, U.S.A., INC.

DC-DC Converter Unit Quality Information

The DC-DC converter supplies stable power to the vehicle when the battery voltage drops during engine restart.If there is a malfunction in the DC-DC converter, a signal is sent to the PCM and either prohibits the auto idle stop operation or engine restart.If the DC-DC converter malfunctions during engine restart, the starter operation continues but the stable power that the vehicle would have received from the DC-DC converter is not supplied.

Simple Circuit Diagram for Description

Courtesy of HONDA, U.S.A., INC.

Pressurization Graphic by the DC-DC converter

Courtesy of HONDA, U.S.A., INC.

Automatic brake hold operating information

The PCM monitors automatic brake hold system statuses and automatically restarts the engine, which has been turned off for auto idle stop, according to system statuses.

Automatic brake hold indicator

Courtesy of HONDA, U.S.A., INC.

ACC with LSF operating information

The auto idle stop system and the ACC with LSF perform the following cooperative control:

While the LSF is in operation, the vehicle stops without depressing the brake pedal and auto idle stop may active.
While the LSF is in operation, restarts the engine automatically when:
- -
  the vehicle in front of your vehicle starts to run.
- -
  the RES/+ button, the SET/- button, or the accelerator pedal is pressed.
- -
  the MAIN switch is turned off.