Diagnostic_Process_Guide - 15

ESSENTIAL TOOLS

Tips for maximizing scan tool use

The scan tool provides a window into what the electronic control unit is seeing.
Here are some tips on maximizing your scan tool use.
by Brandon Steckler, Contributing Editor
Chih Yuan Wu/Dreamstime

E

very journey begins with one
single step. Some people take
that step with their left foot
and others with their right. Neither
would be considered incorrect. One
journey can be carried out a number
of different ways. The point is, there is
no correct or incorrect way to get to a
destination, so long as you get there.
The same holds true regarding diagnostics, or more specifically, analysis. We
can pursue a symptom from multiple
angles. Some technicians have a welldeveloped seat-of-the-pants, instinctivefeel (probably developed from years of
getting their butts kicked in the trenches
of the automotive industry) and can be
fairly accurate in their diagnoses. Other
times, those same technicians make costly mistakes because no true testing was
carried out. Some technicians begin and
end their analysis with the scan tool and
follow their instincts from there. They
employ subsequent tests that focus more
on a particular area of a system, perhaps
giving them the ability to decide what
can't be the source of the fault. This
limits the amount of guessing.
The truth is, if you are not testing,
you are indeed guessing. The scan tool
provides us with a necessary and timesaving preliminary step. The information
from the scan tool does more than display
diagnostic trouble codes (DTCs). It can
also show us what the electronic control
unit (ECU) believes it sees, as well as its
intent, or how it decides to control the
components for the systems it's in charge
of. Following are some techniques I use to
decide where I want to invest my allotted
diagnostic time.

THE ENTIRE STORY
Let's start with parameter IDs (PIDs). The
PIDs a technician views will depend on a
few variables - the first being your scan
tool of choice. Many of the PIDs found
in the OBD generic portion of our scan
tool exist because they are mandated to be
there by law. Many times, we must view
information that is more vehicle-specific,
meaning we may have to view it from the
enhanced side of the powertrain control
module. Not all scan tools are built the
same. If they were, we would have an
extremely expensive device that could
communicate with every node (ECU) on
the network, and support every PID, as
well as every bidirectional control. This
is certainly not the case. I have a few scan
tools I employ regularly. I find where one
of them falls short, the other can fill in
the gap.
Another variable is the loop-speed,
or the speed in which the scan tool can
refresh. When we select to view a set of
PIDs, we are making an inquiry to the
ECU for each PID we select. The ECU
will have to process the request from the
scan tool and then reference the inputs

it's processing from the vehicle. It will
then report the data to the scan tool,
where it's processed and delivered to us
for viewing. All of this takes time - the
more inquiries we make, the slower the
scan tool performs ... so choose wisely.
Next, consider the vehicle system you
are addressing. Some systems are simple
and may involve one or two ECUs to carry
out the process of opening and closing
them. Other systems are very interdependent upon one another (like ADAS,
traction control, or even HVAC) and
require communication between several
ECUs and many times over multiple communication networks. I'm always looking
for the scan tool to tell the entire story. I
should be able to capture the inputs to the
ECU, as well as the outputs to reflect what
the ECU sees and if the ECU is trying to
generate an output. The data should be
collected in a fashion that a fellow technician could analyze the capture and make
a diagnostic decision.
Last, but certainly not least, it helps
to have a thorough understanding of the
system and components that are being
addressed. The ability to analyze scan
December 2020 I Diagnostic Process I 15



Diagnostic_Process_Guide

Table of Contents for the Digital Edition of Diagnostic_Process_Guide

Why Shops Need a Diagnostic Process
How to Establish a Step-by-Step Diagnostic Process
Data From a Distance
Developing a Diagnostic Game Plan
Tips for Maximizing Scan Tool Use
Beyond the Repair
Diagnostic Products
Diagnostic_Process_Guide - 1
Diagnostic_Process_Guide - 2
Diagnostic_Process_Guide - 3
Diagnostic_Process_Guide - Why Shops Need a Diagnostic Process
Diagnostic_Process_Guide - 5
Diagnostic_Process_Guide - How to Establish a Step-by-Step Diagnostic Process
Diagnostic_Process_Guide - 7
Diagnostic_Process_Guide - Data From a Distance
Diagnostic_Process_Guide - 9
Diagnostic_Process_Guide - 10
Diagnostic_Process_Guide - 11
Diagnostic_Process_Guide - Developing a Diagnostic Game Plan
Diagnostic_Process_Guide - 13
Diagnostic_Process_Guide - 14
Diagnostic_Process_Guide - Tips for Maximizing Scan Tool Use
Diagnostic_Process_Guide - 16
Diagnostic_Process_Guide - 17
Diagnostic_Process_Guide - Beyond the Repair
Diagnostic_Process_Guide - 19
Diagnostic_Process_Guide - Diagnostic Products
Diagnostic_Process_Guide - 21
Diagnostic_Process_Guide - 22
Diagnostic_Process_Guide - 23
Diagnostic_Process_Guide - 24
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