Honda Pilot: Auto Idle Stop System Description

Overview

Auto idle stop system is a system that stops an engine (warmed-up condition) when a vehicle stops, and it is determined by the driver's operation, the environment in the cabin and outside of the vehicle, the condition of the vehicle. The auto idle stop system can improve the fuel efficiency and reduce the idling noise.

The auto idle stop system and active control engine mount (ACM) system are performed coordinated control, in order to reduce the vibration when the engine restarts.

The auto idle stop is enabled when pressing the brake pedal with the vehicle stop. During idling stops, the auto idle stop indicator (green) is indicated on the gauge control module.

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.

Operation

The followings show the flow chart for the auto idle stop system control.

The auto idle stop system determines whether the idling stop or restarting engine is needed from informations how the driver's operation, environments of the cabin/outside of the vehicle, and the vehicle conditions are.

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.

At restart

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.

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.

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 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.

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.

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 the auto idle stop system is turned to off by the idle stop off switch, the auto idle stop indicator (amber) comes on

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.

Dropped 12 Volt Battery Voltage:

Boosted 12 Volt Battery Voltage:

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.

Malfunctions disabled the auto idle stop		Warring light
Item	Conditions
System Malfunction	Malfunctions in the auto idle stop system. (PGM-FI (Including the DC-DC converter and the 12 volt battery sensor), the climate control system and the brake system (the negative pressure monitoring) ).
	Malfunctions in the charging system
	Malfunctions in the starter system
	Malfunctions in the PGM-FI system*
	Malfunctions in the A/T control system*
	Malfunctions in the EPS control system
	Malfunctions in the VSA (ABS) system*
	Malfunctions in the VSA system*
	Malfunctions in the brake system*
	Malfunctions in the SRS system*

*: Ever if above indicators are displayed, the auto idle stop system may be enabled according to the contents of malfunction.

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