KOEO & KOER Codes

KOEO and KOER DTCs indicate faults are present at time of testing. A hard fault may cause Malfunction Indicator Light (MIL) to go on and remain on until fault is repaired. The MIL is located on instrument panel and may be labeled SERVICE ENGINE SOON or CHECK ENGINE. If KOEO or KOER codes are retrieved during KOEO ON-DEMAND SELF-TEST or KOER ON-DEMAND SELF-TEST, use DIAGNOSTIC TROUBLE CODE REFERENCE CHARTS  to find appropriate system test to perform.