Fail Safe Operation

Crank Angle Sensor Malfunction:

CIRCUIT OPERATION
The ECU will substitute the input signals for the crank angle sensor, air flow meter, engine temperature sensor, knock sensor and the throttle sensor if the circuits fail. It will also compensate for a malfunction in the main CPU if it develops errors in the computation function. This will allow the vehicle to driven until repairs can be made.
NOTE: The engine will operate at reduced capacity.

AIR FLOW METER MALFUNCTION
If the ECU senses that the air flow meter output voltage is out of the normal range it will substitute the throttle sensor signal for the correct signal. Engine rpm will be limited to 3000 in order to inform the driver that the ECU is in the "Fail-Safe Mode". Refer to the figure above for operating conditions.

Engine Temperature Sensor Malfunction:

ENGINE TEMPERATURE SENSOR MALFUNCTION
When the ECU senses that the engine temperature output voltage is out of the normal range, it will substitute voltage at preset values. Refer to figure above for operating conditions.

THROTTLE SENSOR MALFUNCTION
When the ECU senses that the air temperature sensor voltage is out of the normal range it fix the temperature value at 20° C (68° F).

KNOCK SENSOR MALFUNCTION
When the ECU senses that the knock sensor output signal is out of the normal range it will retard the timing according to operating conditions.

COMPUTATION MALFUNCTION
When the ECU senses that the main computation function (used for mixture ratio self-learning) it will maintain the fuel mixture according to the value stored in the read only portion of the ECU.

Air Flow Meter Malfunction:

Refer to the chart above for fail-safe operating conditions.