Reading Self-Test Codes

Service codes are transmitted on the Self-Test Output and are shown as voltage pulses on a Volt-Ohmmeter (VOM). Key On/Engine Off (KOEO) tests will show three groups of codes. The first group of codes is On Demand, the second group of codes is a Separator code and the third group of codes is the Continuous codes.

NOTE: Procedures in the TESTING section of this article are not in absolute numerical order. Procedures not related to this engine have been removed to eliminate confusion.

The On Demand code first digit is indicated by a pulse, then the needle drops to zero for 2 seconds, then the second digit of the code is displayed. Between service codes 4 seconds will elapse. At the end of the On Demand codes, 6 seconds will elapse. Then the Separator code will be displayed for 1/2 second. After 6 seconds, the first digit of the Continuous code will be displayed, the needle will drop to zero for 2 seconds, then the second digit of the Continuous code will display. At the end of the Continuous codes, all codes will be repeated. After codes have been repeated, Key Off - Engine On.

Key On/Engine Running (KOER) tests will display codes in the same manner, except there will be an Engine ID code, a Dynamic Response Code and an the On Demand codes. The Engine ID code has no application in the field, and is for factory use only. The codes will be displayed in the same manner as Key On -Engine Off codes.