PCM Fail-safe/Back-up Functions

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

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

When an abnormality occurs in a signal from a sensor, the PCM supplies ground for the MIL and stores the DTC in erasable memory. When the ignition is initially turned ON (II), the PCM supplies ground for the MIL for two seconds to check the MIL bulb condition.

The PCM lights the low fuel indicator light and informs the driver that the fuel level is low.

The PCM calculates the gas quantity in the fuel tank by using the fuel pressure value detected by the fuel tank pressure sensor and the fuel temperature value detected by the fuel tank temperature sensor, and outputs the signal to the gauge assembly.

When the PCM detects a malfunction of the fuel tank pressure sensor and/or fuel tank temperature sensor, the PCM blinks the low fuel indicator light and causes the fuel gauge to read empty.

When the PCM detects a gas leak, the PCM blinks the low fuel indicator light and reduces the fuel meter to 0.

If the engine is stopped while the low fuel indicator light is blinking, the engine will not start until the PCM is reset.

To prevent false indications, the Two Trip Detection Method is used for the HO2S, fuel metering-related, idle control system, ECT sensor and EGR system 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 informs the driver by lighting the MIL. However, to ease troubleshooting, this function is cancelled when you jump the service check connector. The MIL will then blink immediately when an abnormality occurs.

A "Driving Cycle" consists of starting the engine, beginning closed loop operation, and stopping the engine. If misfiring that increases emissions is detected during two consecutive driving cycles, or TWC deterioration is detected during three consecutive driving cycles, the PCM turns the MIL on. However, to ease troubleshooting, this function is cancelled when you jump the service check connector. The MIL will then blink immediately when an abnormality occurs.