Fail-Safe System

PURPOSE
The fail-safe system makes engine starting possible if there is something malfunctioning in the ECCS control module's (ECM's) central processing unit (CPU) circuit. in former models, engine starting was difficult under the conditions mentioned above. But with the provisions provided in this fail-safe system, it is possible to start the engine.

Fail-safe Operation:

OPERATION
When the fail-safe system activates, i.e. if the ECM detects a malfunction condition in the C.P.U. of ECM, the MALFUNCTION INDICATOR LAMP on the instrument panel lights to warn the driver.
When the fail-safe system is operating, fuel injection, ignition timing, fuel pump operation, IACV-AAC valve operation and radiator fan operation are controlled under certain limitations.

FAIL-SAFE COMPONENT MALFUNCTIONS

Engine Coolant Temperature Sensor Malfunction:

ENGINE COOLANT TEMPERATURE SENSOR
When engine coolant temperature sensor output voltage is below or above the specified value, water temperature is fixed at the preset value as shown in image.

KNOCK SENSOR
When the output signal of the knock sensor is abnormal, the ECM judges it to be malfunctioning. When knock sensor is mal- functioning, ignition timing will retard according to operating conditions.

Mass Air Flow Sensor Malfunction:

MASS AIR FLOW SENSOR
If the mass air flow sensor output voltage is above or below the specified value, the ECCS control module (ECM) senses an mass air flow sensor malfunction. in case of a malfunction, the throttle position sensor substitutes for the mass air flow sensor. Though mass air flow sensor is malfunctioning, it is possible to drive the vehicle and start the engine. But engine speed will not rise more than 2,400 rpm in order to inform the driver of fail-safe system operation while driving.

TPS Malfunction:

THROTTLE POSITION SENSOR
When the output signal of throttle position sensor is abnormal the ECCS control module (ECM) judges it as a malfunctioning of throttle position sensor. The ECM does not use the throttle position sensor signal, but judges the idle position by the amount of fuel injected and the engine speed.

CANCELLATION OF FAIL-SAFE SYSTEM WHEN ECM IS MALFUNCTIONING
Activation of the fail-safe system is cancelled each time the ignition switch is turned OFF. The system is reactivated if all of the above-mentioned activating conditions are satisfied after turning the ignition switch from OFF to ON.