On-Board Diagnostic System

PURPOSE



The ECM contains a built-in self-diagnosis system by which troubles with the engine signal network are detected and a malfunction indicator lamp on the instrument panel lights up.
By analyzing various signals as described in "Trouble Code Descriptions", the ECM (ECM) detects system malfunctions relating to the sensors or actuators.

OPERATION

"Normal Mode" Operation
In the Normal Mode, the self-diagnosis system monitors 18 (for California specification vehicles) or 17 (for Federal or Canadian specification vehicles) items, indicated by code numbers (DTC's) as listed under "Trouble Code Descriptions". A malfunction indicator lamp informs the driver that a malfunction has been detected

"Test Mode" Operation
A Test Mode function has been added to the functions of the self-diagnosis system of the Normal Mode for the purpose of detecting malfunctions such as poor contact, which are difficult to detect in the Normal Mode.
In the Test Mode, 12 items (for California specification vehicles ) or 11 items (for Federal and Canadian specification vehicles), indicated by code numbers (DTC's) as described under "Trouble Code Descriptions", are monitored. If a malfunction is detected the ECM lights the malfunction indicator lamp to warn the technician that malfunction has been detected

"Fail-Safe Mode" Operation



If there is trouble with the program in the ECM and the ignition signals (IGT) are not output from microcomputer, the ECM controls fuel injection and ignition timing at predetermined levels as a back-up function to make it possible to continue to operate the vehicle.