The ECM controls the internal fuel pressure of the common rail by opening and closing the pressure discharge valve. When sudden deceleration occurs, the internal fuel pressure will temporarily become higher than usual and combustion noise may result. Therefore the ECM will open the valve temporarily to discharge the excess pressure inside the common rail. Also, the pressure discharge valve opens when the engine switch is turned OFF to allow prompt discharge of the common rail internal pressure.

The mass air flow meter uses a platinum hot wire. The mass air flow meter consists of a platinum hot wire, a temperature sensor and a control circuit installed in a plastic housing. The mass air flow meter works on the principle that the hot wire and temperature sensor located in the intake air by-pass of the housing detect any changes in the intake air temperature.

The actuator in the injector, which operates the nozzle needle, is a piezo type to allow high-speed operation. This high speed injector allows a two stage injection to reduce combustion noise, and allow high power output.

An injector consists of a nozzle needle, two pistons, three-way valve and a piezo actuator.

Disconnect the E70 suction control valve connector.

While the engine is being cranked, the positive battery voltage is applied to terminal STA of the ECM.

If the ECM detects the Starter Control (STA) signal while the vehicle is being driven, it determines that there is a malfunction in the STA circuit. The ECM then illuminates the MIL and sets the DTC.

This monitor runs when the vehicle is driven at 20 km/h (12.4 mph) for over 20 seconds.

The diesel turbo Intake Air Temperature (IAT) sensor is built into the charge air cooler and senses the IAT. A built-in thermistor in the sensor changes its resistance value according to the intake air temperature. The lower the intake air temperature, the greater the thermistor resistance value. The higher the intake air temperature, the lower the thermistor resistance value (see Fig. 1).

This DTC indicates that fuel leaks exist in highly-pressurized areas in the common rail system. The ECM constantly monitors the internal fuel pressure of the common rail after the engine is started. The ECM sets this DTC if the drop in the internal fuel pressure is large when injecting the fuel.

Lexus IS250 IS220d GSE20 ALE20 2AD-FHV ENGINE CONTROL SYSTEM

The ECM sets this DTC if the fuel pressure inside the common rail is more than 200 MPa (2,039 kgf/cm², 29,007 psi). This DTC indicates that: 1) the suction control valve may be stuck open, 2) there may be a short in the suction control valve circuit.

If this DTC is set, the ECM enters fail-safe mode and limits the engine power. The fail-safe mode continues until the engine switch is turned OFF.

While the engine switch is OFF, battery voltage is supplied to terminal BATT of the ECM for storing DTCs and fuel injection feedback learning values.