Fail-Safe Function

When a malfunction occurs within the engine control system, the PCM maintains control over the fuel injection system, the idle speed control system, etc. The PCM controls these systems by using calculated values and backup programs stored within the PCM.

This function is called the fail-safe function. With the fail-safe function, a certain level of engine performance is available even when a malfunction occurs. The fail-safe function prevents a complete loss of engine performance.

The systems covered by the fail-safe function are as follows:

• The engine coolant temperature (ECT) sensor
• The throttle position (TP) sensor
• The mass air flow (MAF) sensor
• The intake air temperature (IAT) sensor
• The vehicle speed sensor (VSS)
• The barometric (BARO) pressure sensor
• The fuel level sensor
• The central processing unit (CPU) in the PCM