Auto Idle Stop System Description

Overview 

Auto idle stop system is a system that stops an engine (warmed-up condition) when a vehicle is stopped. It is determined by the driver's operation, the environment in the cabin and outside of the vehicle and other conditions. The auto idle stop system can improve fuel efficiency and reduce idling noise. The auto idle stop system and active control engine mount (ACM) system work together, in order to reduce vibration when the engine restarts. The auto idle stop is enabled when pressing the brake pedal with the vehicle stopped. During idling stops, the auto idle stop indicator (green) is indicated on the gauge control module. With ACC/LSF system:This auto idle stop system stops the engine automatically when the vehicle stops while using the ACC/LSF system.

When automatic brake hold is not activated and the ACC/LSF system is not activated (with ACC/LSF system): Restarts the engine automatically after releasing the brake pedal, and also automatically restarts the engine by the driver operations, environments of the cabin/outside of the vehicle, and the vehicle conditions without releasing the brake pedal.

When automatic brake hold is activated: Restarts the engine automatically when the accelerator pedal is pressed after releasing the brake pedal, and also automatically restarts the engine by the driver operations, environments of the cabin/outside of the vehicle, and the vehicle conditions without pressing the accelerator pedal after releasing the brake pedal.

When ACC/LSF system is activated (With ACC/LSF system): Restarts the engine automatically after the vehicle detected in front of your vehicle starts again, and also automatically restarts the engine by the driver operations, environments of the cabin/outside of the vehicle, and the vehicle conditions.

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Operation 

When ACC/LSF system is not activated (with ACC/LSF system) 

The followings show the flow chart for the auto idle stop system control. The auto idle stop system determines whether the idling stop or engine restart is needed from the driver's operation, environments of the cabin/outside of the vehicle, and the vehicle conditions.

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When ACC/LSF system is activated (With ACC/LSF system) 

If the engine is stopped by the brake control while the ACC/LSF is in operation, the idling stop function continues after releasing the brake pedal. While in idling stop, and if you press the accelerator pedal, the SET button, or the RES+ button, the engine will restart automatically. While in idling stop, if the ACC combination switch (MAIN) is turned to OFF, the engine will restart automatically and the brake control will stop.

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Control 

At auto idle stop 

The powertrain control module (PCM) determines whether activating the auto idle stop or not by signals from each unit, sensor, and switch. When the PCM determines that the conditions are met for the auto idle stop system, the PCM stops the engine by cutting the fuel injection, and also enables the starting assist brake function to operate. While the auto idle stop is operating, the auto idle stop indicator (green) on the gauge control module lights, and the low oil pressure indicator and the charging system indicator go off.

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At restart 

When automatic brake hold is not activated and ACC/LSF system is not activated (with ACC/LSF system): When the vehicle speed condition is met and the brake pedal is pressed, the engine stops automatically. Release the brake pedal to restart the engine.

When automatic brake hold is activated: When the vehicle speed condition is met and the brake pedal is pressed, the engine stops automatically. Press the accelerator pedal after releasing the brake pedal to restart the engine.

When the ACC/LSF system is activated (with ACC/LSF system): When the vehicle speed condition is met and the preceding vehicle is stopped, the engine stops automatically. Press the SET button, the RES+ button, or the accelerator pedal, to restart the engine.

The PCM determines engine restarting by signals from each unit, sensor, and switch. According to the signal, the PCM restarts the engine by resuming fuel injection and driving the starter motor.

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With Climate Control 

To keep comfort in the cabin during the auto idle stop, the climate control unit sends the signals to the PCM that are sent from each sensor and switch. Those are "enable to idle stop", "disable to idle stop", "need to engine restart". When the PCM requests to restart the engine during auto idle stop from the climate control unit, the PCM restarts the engine automatically, and the auto idle stop indicator goes off. Time that the engine has stopped has been extended by adopting the cold storage evaporator. When the climate control unit malfunctions, malfunction information is transmitted to the PCM and the auto idle stop indicator (amber) blinks.

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12 Volt Battery Deterioration Detection 

The PCM receives information which are the 12 volt battery internal resistance, temperature, current, and voltage via the F-CAN from the gauge control module. The PCM detects the 12 volt battery deterioration condition based on the received information. If the PCM determines that the 12 volt battery is deteriorated, it disables the auto idle stop.

After replacing the 12 volt battery, reset the 12 volt battery internal resistance value by the 12 volt battery internal resistance reset procedure.

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Number of Starter Operations 

PCM counts the number of starter operations.

If the number of starter motor operations exceeds the setting limit, the auto idle stop is disabled, and the auto idle stop indicator (amber) blinks*. In this case, both starter motor and starter cut relays need to be replaced. When replacing the starter motor and the starter cut relays, it is need to clear the counter of "STARTER and STARTER CUT RELAY" with the HDS.

When replacing the PCM, the number of starter motor and starter relays operations, those are stored in previous PCM, need to be transferred to the new PCM.

*: When the auto idle stop system is turned to off by the idle stop off switch, the auto idle stop indicator (amber) goes off.

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With DC-DC Converter 

The DC-DC converter boosts the voltage to compensate for voltage loss that occurs when restarting the engine, in order to provide a stable power supply to each electrical component of the vehicle. The DC-DC converter is activated by a start signal from the PCM.

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

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Malfunctions related to the auto idle stop system 

When the system related to the auto idle stop system (refer to the following) is fault, the auto idle stop system is prohibited. If the following indicator blinks or comes on, do the troubleshooting for each related system.

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