Overview of Three Digit EEC-IV Self-Test Codes

Ford introduced three digit EEC-IV Self-Test codes in 1991 to accommodate the increasing number of service codes required to support various government On-Board Diagnostic (OBD) regulations. The phase in from two digit to three digit codes started in the 1991 model year and is largely complete except for some medium/heavy trucks that will retain two digit codes through the 1994 model year.

MIL LAMP ACTIVATION

Following is a list of reasons why a technician may see the MIL lamp lit with no accompanying Continuous Memory Self-Test codes.