KOEO & KOER Codes (Hard Faults)
WARNING: This page is about a different car, the 1995 Ford Windstar. However, it is still accessible from the selected car via links, so may be relevant.
These codes indicate faults are present at time of testing. A hard fault may cause CHECK ENGINE or Malfunction Indicator Light (MIL) to go on and remain on until fault is repaired. If KOEO or KOER codes are retrieved during KOEO SELF-TEST or KOER SELF-TEST, use DIAGNOSTIC TROUBLE CODE REFERENCE CHARTS to find correct testing and repair procedures.