On-Board Diagnostic System

The engine control module monitors the input/ output signals (some signals at all times and the others under specified conditions) of the engine control module.

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 engine control module judges that an irregularity has occurred, memorizes the diagnostic trouble code, and outputs the signal to the diagnostic output terminal.

There are 16 diagnostic items, including the normal state, and the diagnostic results can be read out with a scan tool.

Moreover, since memorization of the diagnostic trouble codes is backed up directly by the battery, the diagnostic results are memorized even if the ignition key is turned off. The diagnostic trouble codes will, however, be erased when the battery terminal or the engine control module connector is disconnected.

In addition, the diagnostic trouble code can also be erased by turning the ignition switch to ON and sending the diagnostic trouble code erase signal from the scan tool to the engine control module.

Caution If the sensor connector is disconnected with the ignition switch turned on, the diagnostic trouble code is memorized. in this case, send the diagnostic trouble code erase signal from the scan tool to the engine control module and the diagnostic memory will be erased.

The 16 diagnostic items are provided as follows, and if plural items are activated, they are all indicated sequentially from the smallest code number.

Caution The diagnostic trouble code of ignition timing adjustment signal is outputted when terminal for ignition timing adjustment is grounded. Therefore, it is not abnormal that the code is outputted even when terminal for ignition timing adjustment is grounded for ignition timing adjustment.