Fail-safe and Back-up Function 2 of 2


Back-up Function
The back-up function switches over to fixed signal control by the back-up IC to permit driving in cases when a malfunction occurs in the microcomputer inside the engine ECU. The back-up function only controls basic functions, so it is unable to provide the same level of engine performance as when the engine is operating normally.
1. Operation of the back-up function
The engine ECU switches to back-up mode if the microcomputer is unable to output the ignition timing (IGT) signal. When back-up mode is executed, the fuel injection duration and ignition timing are activated at their respective fixed values in response to the starter signal (STA) and IDL signal. The MIL also lights up to inform the driver of a malfunction. (The engine ECU does not record a DTC.)



Fuel injection duration

Ignition timing


20.0 ms



3.5 ms



6.0 ms

(Values in the list vary by model.)

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