On-Board Diagnostics - First Generation (Obd 1) - Innova 3100 Owner's Manual

The computer compares the values received from these sensors with
its preset reference values, and makes corrective actions as needed
so that the sensor values always match the preset reference values
for the current driving condition. The computer makes adjustments by
commanding other devices such as the fuel injectors, idle air control,
EGR valve or Ignition Module to perform these actions.
Vehicle operating conditions are constantly changing. The computer
continuously makes adjustments or corrections (especially to the
air/fuel mixture and spark timing) to keep all the engine systems
operating within the preset reference values.

On-Board Diagnostics - First Generation (OBD 1)

With the exception of some 1994 and 1995 vehicles,
most vehicles from 1982 to 1995 are equipped with
Beginning in 1988, California's Air Resources Board
(CARB), and later the Environmental Protection Agency
(EPA) required vehicle manufacturers to include a self-
diagnostic program in their on-board computers. The
program would be capable of identifying emissions-related
faults in a system. The first generation of Onboard
Diagnostics came to be known as OBD 1.
OBD 1 is a set of self-testing and diagnostic instructions programmed
into the vehicle's on-board computer. The programs are specifically
designed to detect failures in the sensors, actuators, switches and
wiring of the various vehicle emissions-related systems. If the
computer detects a failure in any of these components or systems, it
lights an indicator on the dashboard to alert the driver. The indicator
lights only when an emissions-related problem is detected.
The computer also assigns a numeric code for each specific problem
that it detects, and stores these codes in its memory for later retrieval.
These codes can be retrieved from the computer's memory with the
use of a "Code Reader" or a "Scan Tool."
OBD 2
Learning More
COMPUTER ENGINE CONTROLS
OBD 1 systems.
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