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Getting Started
2
SAE Publications
SAE has published hundreds of pages of text defining a standard
communication protocol that establishes hardware, software, and
circuit parameters of OBD II systems. Unfortunately, vehicle
manufacturers have different interpretations of this standard
communications protocol. As a result, the generic OBD II
communications scheme varies, depending on the vehicle. SAE
publishes recommendations, not laws, but the Environmental
Protection Agency (EPA) and California Air Resources Board (CARB)
made many of SAE’s recommendations legal requirements that vehicle
manufacturers were required to phase in over a three-year period.
Beginning in 1994, vehicles with a new engine management computer
( about 10% of each manufacturers fleet ) were supposed to comply
with OBD II standards. For 1995, OBD II systems were to appear on
about 40% of the new vehicles sold in the United States. Some of the
1994-1995 OBD II systems were not fully compliant, so the Government
granted waivers to give manufacturers time to fine-tune their systems.
Beginning in 1996, most of the new vehicles sold in the United States
were fully OBD II compliant.
The tables below highlight changes for GM, Ford, and Chrysler. If this
seems confusing, don’t worry. The Scan Tool makes it easy. Based on
the vehicle identification (VIN) information selected during Scan Tool
setup, the vehicle 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 Data LInk
Connector on page 2-9.
GM On-Board Diagnostics
System Years Description
OBD I Control Module
1981–1995
Most vehicles used the 12-pin ALDL (Assembly Line Data Link)
located under the dash on the driver side. Some 94-95 vehicles
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.
OBD II Control Module
1994*-Present Complies with OBD II regulations and uses the J1962 DLC.
*
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.