7
Diagnostic Screen
Whenever the engine detects a problem, it activates the Check Engine
light on the dashboard. At the same time it transmits a series of codes which
a mechanic can pick up using his “scan tool”. The VMS also picks up those
codes, stores them, and translates them for you to read. You can display this
information whenever the Check Engine light come on by pressing
D
iag
and
activating the Engine Diagnostics Screen.
Note that the VMS can only report what the engine transmits. Problems
that are external to the engine may not show up, or may show up in an indirect
form. For example, a bad alternator will likely not be immediately detected.
But eventually a low voltage condition will probably be detected and displayed.
Internal engine problems are much easier to detect, and are generally very
precise.
Press
D
iag
to activate the Engine Diagnostic Screen, which shows cur-
rent engine problems at the top
and the Engine Diagnostic His-
tory , which displays a history
of engine problems.
Engine Diagnostic Section
The top section of the
screen shows any diagnostic
messages received since the
VMS was turned on. The
“scan code” is displayed, along
with a plain language interpre-
tation of the code. The VMS
does not have to be on this
screen to receive and store
diagnostic messages. You can activate this screen at any time to see all
codes that have been generated since the VMS 645 was turned on. The unit
can store up to six codes at a time.
Press
C
lear
to clear out the list of codes. If a problem is still occurring, it
should reappear in a few moments.
Engine History Section
This screen shows every diagnostic message ever received by the VMS
645. It also shows the date, odometer reading, engine RPMs, engine load,
and temperature at the time the fault first occurred. The VMS only stores
the first occurrence of each message, unless the codes were cleared on the
Engine Diagnostic Screen. The code will be recorded each time the problem
reoccurs after having been cleared on that screen.
The list will display the most recent messages at the top. The history
can be cleared using a hidden screen. See the appendix.
Use the
K
nob
to scroll through the history.
