General Information

ON-BOARD DIAGNOSTIC SYSTEM
The On-Board Diagnostic system is so designed that the circuits handling the input signals from the sensors and output signals for driving actuator are continuously monitored by the Engine Control Module (ECM). In the event of a failure, the ECM stores it in memory and operates the malfunction indicator lamp (MIL) on the instrument panel when the nature of trouble is important, to warn the operator of failure.

NOTE: The On-Board Diagnostic system is capable of troubleshooting the electric circuits in the Closed Loop Emission Control system only and does not cover the trouble in the sensors, actuators or the engine itself.





Warning to Operator
When a failure has developed in the following systems while driving, the malfunction indicator lamp within the instrument panel is operated to warn the driver of system failure.

^ Mass air flow sensor system
^ Engine coolant temperature sensor system
^ Vehicle speed sensor system
^ Heated oxygen sensor system
^ Fuel injector system
^ ECM

A Diagnostic Trouble Code (DTC) will be stored in Engine Control Module (ECM) memory. As long as a problem is present, the light will remain "ON" while the engine is running. If the problem is intermittent, the light will go out but a DTC will be stored in ECM memory. As a bulb check, the MIL will come "ON" with the ignition switched "ON" and the engine not running. If no codes are present, the light will go out upon starting the engine. If the light remains "ON," the system has detected a fault.




Diagnostic Trouble Code (DTC) No. Display
1. When the DTC test lead in the vicinity of the ECM is connected with the ignition switch turned to ON position, the diagnostic trouble code stored in memory is displayed in the malfunction indicator lamp.

2. With the engine not in operation, first, the DTC 12 is indicated three times, which means that the ECM is functioning normally. Then other DTCs indicating other malfunctions, if any, come on three times each in the ascending order of DTC numbers.

3. The malfunction DTCs are also read out when the engine is running. In this case, the DTC 12 is not indicated.