Key On Engine Off (KOEO) Self Test Description

The Key On Engine Off (KOEO) portion of the self-test looks for normal engine OFF sensor readings. Any sensor that is out of limits, open, or shorted will set an on-demand or hard fault code. If all sensors are within expected ranges, a code 11 will be displayed. Codes are repeated to make it easier for the technician to verify the code sequence. After the hard fault codes, a single pulse (displays as a 10) occurs to signal that the next set of codes will be from the continuous test.
The continuous self-test monitors sensor inputs during normal operation, and stores information in a special memory called Keep Alive Memory (KAM) when errors are detected. Generally, checks are made only for open or shorted circuits. In a few cases, improper sensor readings are noted. For example, if a coolant temperature sensor should change from cold to hot to cold in too short a period of time, an error is noted. When the number of errors in a given time period exceeds a pre-determined number, that code is stored in KAM. This means that the error will have to be seen several times by the computer before it will register. This helps prevent codes from being incorrectly set on components that are actually good. Codes indicating faults that have not occurred in 40-80 engine warm-up cycles are automatically erased from KAM. Continuous fault codes can also be manually erased by opening the STI circuit while codes are being displayed. Continuous test codes are issued using the same format as the hard fault codes, and are also repeated.
Finally the test enters the output state test, which simply activates the actuator outputs ON and OFF based on requests from the person performing the test.