Auto Idle Stop System Description (2021 2022)

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 environmental 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 the 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 the certain conditions are not met, the auto idle stop suspend 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 (During auto idle stop: Green) 

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Auto Idle Stop OFF Indicator 

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Auto Idle Stop Suspend Indicator 

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Auto Idle Stop System Indicator (On malfunction: Amber blinks) 

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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)) 

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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 the PCM 

Target unit, sensor and switch	Transmitting Signal	Received Signal	Remarks
Related control units	System malfunction signal*	-	See detailed information of the Control or Communication Signal
Idle stop off switch	Auto idle stop cancellation signal	-	-
Snow switch	Snow switch signal	-	-
Hood latch switch	Hood open/close signal	-	-
Driver's seat belt switch	Seat belt latched/unlatched signal	-	-
EPS control unit	Steering torque signal Steering torque signal Steering angle information	-	-
SBW shifter control module	Shift position information	-	-
TCM (Countershaft speed sensor)	Output shaft (countershaft) speed (vehicle speed) 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.
TCM (ATF temperature sensor)	ATF temperature 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.
TCM	Transmission status information Execution/prohibition signal of the auto idle stop	Engine status information Engine speed	-
SBW shifter control module	Shift position information	-	-
Brake pedal position switch	Brake pedal on/off signal	-	-

*: See detailed information

Target unit, sensor and switch	Transmitting Signal	Received Signal	Remarks
VSA modulator-control unit	Hydraulic control operating information Vehicle speed information Master cylinder pressure information* Starting Assist Brake Function information Vehicle inclination angle information Automatic brake hold system operation information	Starting Assist Brake request signal	See detailed 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 temperature 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*	See Detail Information of the Control or Communication Signal
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
DC-DC converter	Unit quality information*	-	See detailed 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: Auto idle stop suspend indicator is turned on 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 idle stop system off switch is on: Auto idle stop off indicator is turned on When there is a failure of the idle stop system: Auto idle stop system indicator (amber) blinks
Injector	-	Fuel injection stop/injection command signal	-
Fuel pump	-	Fuel pump ON/OFF command signal	-
Alternator	-	Alternator operating command	-

*: See detailed information

Detail Information of the Control or Communication Signal 

System Malfunction Signal 

If there is a malfunction in the auto idle system and related systems, the auto idle stop system indicator (amber) will blinks and a message displays in the multi-information display to inform the driver.

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If a malfunction in the following system, the auto idle stop is prohibited.

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 Starter motor has reached maximum cycle count
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.
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.
A/T 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.

System	Warning indicator	Remarks
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
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.
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 contents 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.

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.

Transmitting and received signals to/from the 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 temperature 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	-
Rear A/C control panel	Cabin temperature and air volume setting information	-
Evaporator temperature sensor	Evaporator temperature information	-
Humidity/in-car temperature sensor	Humidity and in-car temperature information in the cabin	-
Sunlight sensor	Sunlight information	-
PCM	-	Auto idle stop implementation/prohibition determination information from 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 auto idle stop system indictor (amber) on the gauge control module blinks.

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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). The 12 volt battery internal resistance information is memorized in the PCM.

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 

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Pressurization Graphic by the DC-DC converter 

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Idle Stop Message Indication 

If the auto idle stop is prohibited by the vehicle condition when stop the vehicle, or engine is restarted automatically during the auto idle stop, the idle stop message for the prohibition or the restart is displayed in the multi-information display for several seconds. The message can be turned on or off by pressing and holding the auto idle stop OFF switch.

Message	Vehicle Condition* 1
Courtesy of HONDA, U.S.A., INC.	When auto idle stop cannot be performed due to the following conditions Transmission temperature is out of specified Estimate 12 V battery temperature is lower than specified Stopping the vehicle on a steep slope Auto idle stop cannot be performed for some reason other than the above
Courtesy of HONDA, U.S.A., INC.	When the engine restarted automatically due to the following conditions Press and release the brake pedal repeatedly Transmission fluid temperature is out of specified Engine restarted automatically for some reason other than the above
Courtesy of HONDA, U.S.A., INC.	When auto idle stop cannot be performed due to the following conditions Engine coolant temperature is out of specified
Courtesy of HONDA, U.S.A., INC.	When auto idle stop cannot be performed due to the following conditions Engine was started with the hood open 12 V battery charging condition is out of specified When the engine restarted automatically due to the following conditions 12 V battery discharging condition is high Estimate 12 V battery temperature is lower than specified
Courtesy of HONDA, U.S.A., INC.	When auto idle stop cannot be performed due to the following conditions During the climate control system control, the cabin temperature difference between commanded versus actual is large Windshield defrost is used When the engine restarted automatically due to the following conditions During the climate control system control, the cabin temperature difference between commanded versus actual is large Windshield defrost is used

*1: Refer to the Available Conditions and Engine Restart Conditions for Auto Idle Stop .

Message	Vehicle Condition* 1
Courtesy of HONDA, U.S.A., INC.	When auto idle stop cannot be performed due to the following conditions Shift position is other than D position
Courtesy of HONDA, U.S.A., INC.	When auto idle stop cannot be performed due to the following conditions Brake pedal pressing force is insufficient (auto idle stop can be performed by further depressing the brake pedal)
Courtesy of HONDA, U.S.A., INC.	When auto idle stop cannot be performed due to the following conditions Snow switch is turned to ON

*1: Refer to the Available Conditions and Engine Restart Conditions for Auto Idle Stop .