Professional Distributor - 34

DIAGNOSTIC TECH
commercials and online ads promoting free diagnostics.
Technicians usually connect a scan
tool when there is a problem with the
vehicle. In my shop, however, every
vehicle that comes in for routine service
gets a full scan, or what is otherwise
known as a Health Check. More on the
term "Health Check" later in this article. When a technician is addressing a
problem, the first thing that I believe
most do is query all vehicle controllers
(ECM, PCM, TCM, etc.) for DTCs.
With codes in possession, what do
you do? In my personal view (and I
believe many of my colleagues would
agree), the DTC only tells part of the
story; there is a ton of diagnostic
data that should be gathered before
moving on.
OBD-II vehicles offer up a number
of additional clues through Mode$01
(live data), Mode$02 (freeze frame),
Mode$06 (diagnostic test results),
Mode$09 (in-use performance testing), and so on. These are quite helpful in aiding the technician who is
essentially tasked with being a "scientific diagnostic investigator," as my
colleague and friend Jorge Menchu
from Automotive Electronic Services
would say.
This is where freeze-frame can
be very helpful in surfacing clues. In
one recent case we had at my shop, a
vehicle arrived with a complaint of a
flashing malfunction indicator light
(MIL) and running rough. The following DTCs were stored: P0300, P0302,
P0304, and P2198.
When the freeze-frame was
reviewed for the P2198, two indicators
provided further clues to help begin
to form a hypothesis. The glaring clue
I observed was that the bank 2 longterm and short-term fuel trim values,
together, accounted for more than a 40
percent subtraction of the determined
fuel delivery from that bank. What we
discovered was that the B2S1 HO2S
was mis-reporting a rich condition,

which resulted in the ECM leaning
out bank 2 to the point where lean
misfires began to occur.
One should have a process in
place that allows them to structurally
organize this information. My recommendation is to store these within the
work order. Many shop management
systems allow for technician notes,
and some even store scan tool reports,
pictures, videos, and more.
When you're assembling your
data, think about how the data will tell
the story about the vehicle's state of
health to the customer. Doing so will
help improve your customer communications and help everyone involved
understand the vehicle condition and
needed services.
I think we can all agree that there
isn't an "easy button" (and I don't think
there ever will be) on the scan tool.
This is because the automobile is
one of the most sophisticated devices
anyone will ever use in their lifetime.
Therefore, these complicated devices
actually require skilled technicians to
carry out the appropriate test routines
when performing diagnostic analysis.
I believe that one should always
operate forensically prior to performing any intrusive testing. Adherence
to this discipline can save time in the
long run. It's been my experience that
oftentimes the client brings the vehicle
in well after the MIL first appeared,

34 Professional Distributor I May 2020 I VehicleServicePros.com

The MAHLE TechPRO, a PC-based scan tool,
allows technicians to produce scan reports.

which can complicate matters.
When documenting your findings before commencing repairs, you
now have a record of existing state of
health. This rings especially true on
vehicles possessing both persistent
and intermittent DTCs. Your log is a
crucial aspect to the repair process;
after addressing the persistent DTC
through repairs, subsequent scans
may result in clearing multiple DTCs.
Having this information will provide a clear picture to the customer
of the entire repair process, as well
as an understanding that should the
MIL illuminate down the road and a
previously active DTC presents itself,
it is not a returning issue, but rather a
new repair to be addressed. It's fair to
assume that all professionals want to
return a vehicle to service in the highest roadworthy condition possible, and
when one is presented with a plethora
of DTCs, we can only fix what we see
and validate as broken at the time.
When it comes to choosing a scan
tool, one needs to become highly
familiar with the tool's strengths and
weaknesses. Even at the OEM level,
some of their tools make it difficult to
obtain the information the technician
needs quickly. Oftentimes, I find that
the OBD-II generic information is all
I need to begin painting the picture.

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