enblethen wrote:
Found this on another website
the F53 chassis in 1997 was still running EEC IV engine control system due to the GVW of the vehicle exempting it from OBDII requirements. You'll find the EEC IV (DLC) connector on the passenger side near the starter relay. Location varies since coach builder may move it, but should be in that area.
OBD-II became mandatory on a "light duty" vehicles in 1996MY. EEC-V came out about that time. It was necessary to contain all of the extra code mandated by the government.
EEC-IV was carried forward on vehicles that did not require OBD-II for a few years (Lower cost.)
Today, more than 50% of the software in a typical PCM is for diagnostics and monitoring.
