About import vehicle diagnostic systems – Equus 3173 - Import Code Reader User Manual
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About Import Vehicle Diagnostic Systems
ON-BOARD VEHICLE DIAGNOSTICS (OBD I)
Chapter 2
10
NOTE:
The computer does not make the adjustments or
corrections directly. It commands other devices such as the fuel
injectors, idle air control, EGR valve or Ignition Module to
perform these functions. These devices are called Actuators
because they initiate an action in response to the commands of
the computer.
ON-BOARD VEHICLE DIAGNOSTICS (OBD I)
•
Beginning in 1988, California’s Air Resources Board
(CARB), and later, the Federal Government's
Environmental Protection Agency (EPA), required
vehicle manufacturers to include a self diagnostic program
capable of identifying an emissions-related fault via the
vehicles On-Board Computers (some manufacturers used
OBD before it was required). The first generation of
Onboard Diagnostics came to be known as OBD I.
•
OBD I is a set of self-testing or self-diagnosing instructions
that are programmed into the vehicle’s on-board computer.
•
The program is specifically designed to detect failures in
the sensors, actuators, switches and wiring of the various
vehicle emissions-related systems (fuel injection system,
ignition system, EGR system, catalytic converter, etc.). If
the computer detects a failure in any one of these
components or systems, it alerts the driver by
illuminating the “Check Engine” light on the dash.
•
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”.
NOTE:
With the exception of some 1994 and 1995 vehicles,
most vehicles from about 1982 to 1995 are equipped with
OBD I systems.
DIAGNOSTIC TROUBLE CODES
Diagnostic Trouble Codes, or Fault Codes, can be used to
identify engine systems or components that are malfunctioning.
The computer records codes for the following two types of
engine problems: