Self-Diagnostic System: Self-Diagnosis

Engine Control Unit (ECU) monitors input/output signals (some signals at all times and other under specified conditions). When it is noticed that an irregularity has continued for a specified time or longer from when the irregular signal is initially monitored, passing a certain number, the ECU judges that an irregularity has occurred, memorizes the malfunction code, and outputs the signal to the self-diagnosis output terminal.

There are 13 diagnostic items, including the normal state, and the diagnosis results can be read out with a voltmeter or multi-use tester. Moreover, since memorization of the malfunction is backed up directly by the battery, the diagnosis results are memorized even if the ignition key is turned off. The malfunction codes will, however, be erased when the battery terminal or ECU connector is disconnected. Malfunction codes are also erased by setting the ignition switch to "ON" position and then sending the malfunction-code-erase signal from the multi-use tester to the ECU.