The ECM continuously monitors its internal memory status, internal circuits, and output signals sent to the throttle actuator. This self-check insures that the ECM is functioning properly. If any malfunction is detected, the ECM will set the appropriate DTC and illuminate the MIL.

The battery supplies electricity to the ECM even when the engine switch is in the off position. This power allows the ECM to store data such as DTC history, freeze frame data and fuel trim values. If the battery voltage falls below a minimum level, these memories are cleared and the ECM determines that there is a malfunction in the power supply circuit. When the engine is next started, the ECM will illuminate the MIL and sets the DTC.

Connect the intelligent tester to the DLC3.

The battery thermometer sensor installed on the battery cover detects battery temperature.

A thermistor is integrated into the battery thermometer sensor, and the resistance in the battery thermometer sensor changes according to the battery temperature.

The resistance of the thermistor in the battery thermometer sensor decreases as the battery temperature increases. The resistance increases as the temperature decreases.

Connect the intelligent tester to the DLC3.

The Mass Air Flow (MAF) meter is a sensor that measures the amount of air flowing through the valve.

The ECM uses this information to determine the fuel injection time and to prove appropriate air-fuel ratio.

Inside the MAF meter, there is a heated platinum wire which is exposed to the flow of intake air.

Refer to DTC P0087 .

The stop light switch is a duplex system that transmits two signals: STP and ST1-. These two signals are used by the ECM to monitor whether or not the brake system is working properly. If the signals, which indicate the brake pedal is being depressed and released, are detected simultaneously, the ECM interprets this as a malfunction in the stop light switch and sets the DTC.

The high-pressure side fuel pump is installed to the cylinder head cover (bank 1) and is driven by the cam located at the rear end of the exhaust camshaft.

The speed sensor detects the wheel speed and sends the appropriate signals to the skid control ECU. The skid control ECU converts these wheel speed signals into a 4-pulse signal and outputs it to the ECM via the combination meter. The ECM determines the vehicle speed based on the frequency of these pulse signals.