Fail-Safe Function

When a malfunction occurs within the engine control system, the PCM maintains control over the fuel injection system, idle speed control system, etc. PCM controls these systems by using calculated values and/or 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:

• Mass Air Flow (MAF) sensor.
• Intake Air Temperature (IAT) sensor.
• Throttle Position (TP) sensor.
• HO2S heater circuits.
• Knock Sensor (KS) system.
• Central Processor Unit (CPU) in the PCM.
• Fuel cut-off for ignition system failures.