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LAUNCH Professional 919E User Manual
1.2 On-Board Diagnostics (OBD) II
Note: With the exception of some 1994 and 1995 vehicles, most vehicles
from 1982 to 1995 are equipped with some type of first generation On-Board
Diagnostics.
OBD II is an early warning system designed to monitor engine, transmission,
and emissions control components by performing specic diagnostic test.
When a fault condition is detected, the system captures important data and
activates the “Check Engine” light.
If the light comes on, the vehicle might have a condition that wastes fuel,
shortens engine lift, or causes excessive air pollution. If the problem that
caused the light to come on is addressed, for instance a loose gap is
tightened, the light will go out.
If the light comes on and stays on, a minor engine fault condition is occurring
and should be addressed as soon as possible.
If the light is blinking, a severe engine fault condition is occurring and should
be addressed immediately.
The diagnostic tool connects to the vehicle’s computer system and captures
information that can help identify the fault condition.
1.3 OBD II Denitions
The following terms and their denitions are related to OBD II systems.
Read and reference this list as needed to aid in the understanding of OBD II
systems.
EOBD - European On-Board Diagnostics. Essentially the same as OBD II,
with the same Data Link Connector and Communication Protocols.
Communication Protocols - Allows dierent systems and sensors in a
vehicle to communicate. There are currently ve protocols:
CAN Bus
J1850 VPW
ISO 9141-2
J1850 PWM
ISO 14230 KWP
Powertrain Control Module (PCM) -- The PCM is the OBD II accepted term
for the vehicle’s “on-board computer.” In addition to controlling the engine
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