Step 3.0 Perform KOEO Self-Test: Introduction

The Key On Engine Off (KOEO) test performs two checks for the purpose of obtaining hard codes and history codes. Note that Ford calls hard codes (found during KOEO) "On-Demand" codes, while history codes are called "Continuous Memory" codes.

For the first check, the entire EEC-IV system is tested with power applied and the engine at rest (hence "KOEO"). If a hard failure is found during this check, an On-Demand code is set. Note that On-Demand codes are never stored or retrieved from memory but are created instantly when a hard failure is found during the check. Intermittent faults that are not failing during the check will be overlooked. If no hard faults are found, a "pass" code 11 is displayed.

About 6-9 seconds after a pass code or the last On-Demand code is displayed, a "Separator" code is displayed to identify the end of the first check (the On-Demand part) and the beginning of the second check (the Continuous part). About 6-9 seconds after the single 1/2 second separator pulse the second check will begin.

The second check displays all past failures, intermittent or hard, that the ECA noted while the vehicle was in normal operation. These Continuous codes have been seen and stored by the ECA in the last 40-80 warm-up cycles (so named because the ECA "Continuously" monitors the system). Any fault not reappearing after 40-80 warm-up cycles is purged. If there are no history codes in memory, a pass 11 will be displayed like above.

In summary, expect any On-Demand (hard) codes or a pass code first, a separator code to distinguish the hard codes from the Continuous (history) codes, then the history codes.

One other item. At the start of the KOEO test there is an output from the ECA known as Fast Codes. These codes contain the identical information as the regular service codes but are transmitted at 100 times the normal rate. Some older equipment cannot use these codes because of the high speed. For example, a VOM will typically show a slight deflection of less than 1/2 second. Ignore this fluctuation if applicable.