Fault Detection and Trouble Code Memory Function
ON-BOARD DIAGNOSTICSThe 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 a malfunction has continued for a specified time or longer since the irregular signal is initially monitored, the engine control module judges that a malfunction has occurred.
After the ECM first detects a malfunction, a diagnostic trouble code is recorded when the engine is restarted and the same malfunction is re-detected. However, for items marked with a "*", a diagnostic trouble code is recorded on the first detection of the malfunction.
There are 46 diagnostic items, 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 to the engine control module in order to erase the diagnostic memory.
The 46 diagnostic items are all indicated sequentially from the smallest code number.
The ECM records the engine operating condition when the diagnostic trouble code is set. This data is called "Freeze-frame" data.
This data can be read by using the scan tool, and can then be used in simulation tests for troubleshooting.