Description of On-Board Diagnostics

Fail-Safe Control System:

The ECU will substitute the input signals for the air flow meter, fuel temperature and engine temperature sensors if the circuits fail. It will also assist in engine operation if the ECU's "Calculation Function is judged to be faulty. This will allow the vehicle to driven until repairs can be made.
NOTE: The engine will operate at reduced capacity and the check engine lamp will illuminate.

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 2400 and the check engine lamp will illuminate in order to inform the driver that the ECU is in the "Fail-Safe Mode". Refer to the figure for operating conditions.

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 as follows:
Starting ......... 20° C (68° F)
Running .......... 80° C (176° F)

FUEL TEMPERATURE SENSOR MALFUNCTION
When the ECU senses that the fuel temperature output voltage is out of the normal range, it will substitute voltage at preset values as follows:
Starting ......... 20° C (68° F)
Running .......... 80° C (176° F)