Equus 3145 - Digital Ford Code Reader (1981 - 1995) - Manual (Page 16)

About Diagnostic Systems
HISTORY OF FORD’S EEC SYSTEMS
13 Chapter 2
• The computer also assigns a numeric code (OBD I systems
utilized a 2 or 3 digit code) for each specific problem that it
detects, and stores these codes in it’s memory for later
retrieval. The codes can be retrieved from the computer’s
memory with the use of a device called a “Code Reader” or
a “Scan Tool”.
• In addition to storing Diagnostic Trouble Codes for
detected problems, most Ford computer systems are also
designed to perform special Self Tests in real time, and to
send the test results to the Code Reader as two- or three-
digit Diagnostic Trouble Codes.
NOTE: With the exception of some 1994 and 1995 vehicles most
vehicles from about 1982 to 1995 are equipped with OBD I
systems.
HISTORY OF FORD’S ELECTRONIC ENGINE CONTROL
(EEC) SYSTEMS
1978: Ford Motor Company introduces its first “Electronic
Engine Control (EEC-I)” system. This system was very
limited in the control of engine functions and only controlled
ignition timing, EGR flow and the air pump's injection of air
into the exhaust.
1979: Ford introduces the EEC-II system. This system added
air/fuel ratio control (feedback carburetor), throttle kicker
(controls engine idle speed during start up and AC function)
and canister purge control to the ECC-I system.
1980: Ford introduces the EEC-III system. This system
included all the sensors used by the ECC-II system, with the
addition of a temperature Sensor. In 1981, the ECC-III system
was modified to include controls for the new Electronic Fuel
Injection systems. The EEC-III system was used on some
models of Ford vehicles until 1984.
1980: In addition to the EEC-III system, Ford introduced
another computer control system, called the “Microprocessor
Control Unit (MCU)”. This system was used on a limited
number of Ford vehicles up until 1991.
1983: Ford introduces the “Electronic Engine Control - IV
(EEC-IV)” system. This system is capable of controlling a
larger number of sensors, switches and actuators, and was
used on a greater number of Ford vehicles. The ECC-IV
system was used from 1983 to 1995.
2