Description of On-Board Diagnostics

Electronic Control System

The functions of the fuel and emission control systems are managed by the powertrain control module (PCM).

Fail-safe Function
When an abnormality occurs in the signal from a sensor, the PCM ignores the signal and assumes a pre-programmed value for the sensor that allows the engine to continue to run.

Back-up Function
When an abnormality occurs in the PCM, the injectors are controlled by a back-up circuit independent of the system to permit minimal driving.

Self-diagnosis
When an abnormality occurs in the signal from a sensor, the PCM supplies ground for the malfunction indicator lamp (MIL) and stores the diagnostic trouble code (DTC) in erasable memory. When the ignition is first turned on, the PCM supplies ground to the MIL for 20 seconds to check the MIL bulb condition.

Two Driving Cycle Detection Method
To prevent false indications, the "two driving cycle detection method" is used for some self-diagnostic functions. When an abnormality occurs, the PCM stores it in its memory. When the same abnormality recurs after the ignition switch is turned OFF and ON (II) again, the PCM turns on the MIL.

Low fuel Indicator light
The PCM turns the low fuel indicator light on to inform the driver that the fuel level is low.
The PCM calculates the gas quantity in the fuel tank by using the fuel pressure valve detected by the Fuel Tank Pressure (FTP) sensor and the fuel temperature valve detected by the Fuel Tank Temperature (FTT) sensor, and outputs the signal to the gauge assembly.
When the PCM detects a malfunction of the FTP sensor, FTT sensor and/or fuel pressure regulator switch, the PCM causes the low fuel indicator light to blink and the fuel gauge to read empty.
When the PCM detects fuel leak, the PCM turns the low fuel indicator light on and reduces the fuel meter to 0.