Introduction To On-Board Diagnostics - Actron 9640 User Manual

Getting Started

INTRODUCTION TO ON-BOARD DIAGNOSTICS

The original on-board diagnostics (OBD I) lacked consistency in
communication and interface while allowing different interpretations amongst
vehicle manufacturers. Ford and Chrysler used different types of engine control
computers and data link connectors, and GM varied the trouble codes and
communication protocols from year-to-year.
The tables below highlight changes for GM, Ford, and Chrysler. If this seems
confusing; don't worry. Your tool makes it easy. Based on the VIN information
selected during Scan Tool setup, the processor is automatically recognized. All
you have to do is choose the correct adapter cable and jumper wires (if
necessary). Details on adapter cables and jumper wires may be found in
"Diagnostic Link Connectors (DLC)" on page 2-5
.
System
OBD I Control Module
OBD II Control Module
*
OBD II system is used on certain 1994-1995 vehicles equipped with a 2.2L, 2.3L, 3.8L, 4.3L or 5.7L
engines.
System Long Name
MCU Microprocessor Control Unit 1980 –1991
Electronic Engine Control,
EEC-IV
Fourth generation
Mazda Electronic Control
MECS
System
Electronic Engine Control,
EEC-V
Fifth generation
Powertrain Electronic
PTEC
Controller
* EEC-V OBD II system used in 1994-1995 vehicles equipped with a 3.8L or 4.6L engine.
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GM On-Board Diagnostics
Years
Most vehicles used the 12-pin ALDL (Assembly Line Data Link)
located under the dash on the driver side. Some 94-95 vehicles
1981–1995 used the 16-pin OBD II (J1962) data link connector (DLC), but
use the Historical application software. Refer to the vehicle's
Vehicle Emission Control Information label.
1994*-Present Complies with OBD II regulations and uses the J1962 DLC.
Ford On-Board Diagnostics
Years
1984 –1995
1988 –1995
1994* – present
2000 – present
Description
Description
Used in police vehicles, containing carbureted
engines. Uses the MCU DLC.
Most Ford vehicles equipped with North
American engines. Uses the EEC-IV DLC.
Vehicles equipped with Mazda-sourced engines.
Uses MECS 6-pin and 17-pin DLCs.
Complies with OBD II regulations and uses the
OBD II J1962 DLC.
Complies with OBD II regulations and uses the
OBD II J1962 DLC.
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