Professional_Tool_And_Equipment_News_September_2020 - 28

Scan tools are essential tools
... but not the only tools
The information and products that work alongside your scan tool for a complete repair.
By Barry Hoyland, Contributing Editor

T

hroughout the history
of diagnostic repair,
there's always been one
universal truth: if you
don't have access to a
good scan tool, you're very unlikely
to accurately diagnose a number of
vehicles that come into your shop. In
fact, the majority of your customers
may think all you need to do is hook up
your "thingy" to their car and it will tell
you what's wrong.
Though not impossible, using only
your scan tool will rarely provide you
with a diagnosis; rather, it is a starting
point to begin your testing process. In
this month's column, we'll discuss some
common fault codes, other computercontrolled system failures, and tools
you'll need to perform tests that are necessary to accurately diagnose an issue
after you have obtained the proper codes
with your scan tool.

ISSUE ONE: P0442 FAULT CODE
- SMALL LEAK DETECTED IN
EVAPORATIVE SYSTEM

The easiest check to perform first with
any evaporative system (evap) leak is to
make sure the fuel cap is present and
tightened properly. Even if the cap is
tight, it may be the cause of the leak,
but in this case, someone has already
tightened the cap.
After that easy check, you should
look at the freeze frame data with your
scan tool. This data contains a listing of
what was occurring at the time the code
was set. Depending on the vehicle, some
of the data available may include how
long the engine was running, the engine

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SEPTEMBER 2020

and vehicle speed, engine temperature,
and possibly the fuel level. All of this
information may assist you in determining what caused the fault. Having
it available to you will also enable you
to operate the vehicle under the same
conditions after the repair to make sure
the code doesn't reset.
After you have the freeze frame data,
refer to your vehicle information source
to determine what the enabling criteria
(the operating conditions) are to trigger
the fault code. This is critical if you'll
be performing a drive cycle to verify
your repair.
Most vehicles use similar criteria for
monitoring the evap system and will
need 15 to 85 percent fuel level. If the
fuel level is either above 85 percent or
below 15 percent, the test won't run and
you'll likely spend hours and multiple
drive cycles attempting to validate your

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p Obtaininfg Mode $06 data can assist you in
determining which part of an evap test failed.

repairs without success. These vehicles
also monitor engine and ambient air
temperature. Upon startup, the two
temperatures need to be within 10
degrees of each other. If not, the computer assumes it's not a cold start and
will not perform an evap test.
Another common condition that's
difficult to overcome is the ambient
air temperature. Many vehicles will
not run an evap test if the air temperature is above 104 degrees F or below 32
degrees F. That's because tank pressure
can change drastically either above or
below those temperatures, making leak
detection difficult.
The evap monitor test needs multiple tests to either pass or fail, so your
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