july2023 - 26

DIAGNOS TIC S
Now, because I learned how to look at problems
differently and approach issues more
logically, the answers come much easier.
Instead of feeling exhausted and numb, I
experience a sense of accomplishment after
a successful diagnosis and repair.
Finding a good repair path will help you
avoid the inevitable " diagnostic headache "
you get when exhausting your options one
by one. With the right vantage point and
approach, any resourceful technician can
solve even the most complex problems.
My method of troubleshooting a complex
unit-one that contains many codes within
multiple systems-is to first look at the big
picture. Then put the pieces together, and
use the process of elimination to find your
root cause of failure. This includes reviewing
the driver's concerns and the vehicle's
repair history and code history. The most
important piece is to review the active and
inactive codes within the module to separate
system concerns. The goal is to organize your
systems and use the process of elimination to
find your correct diagnostic and repair path.
It is important to treat active fault codes
Photo courtesy of Missy Albin
Don't distress;
de-stress your
diagnostic process
Troubleshooting a truck can be a
stressful situation, but following a few
simple diagnostic steps will lead to
faster uptime and fewer headaches.
By Missy Albin
SR. LEAD MASTER TECHNICIAN, TAYLOR AND LLOYD
Missy Albin has been recognized by International Trucks
as " one of the best technicians in the network " and is
the OEM's Female Technician Ambassador for the Tech
EmPowerment recruitment program. She began working
on diesel trucks in 2004 and joined International in 2009
at an IC dealership. While pregnant in 2017, Albin continued
to work in the shop and even earned her Master
Truck Certification during that time.
Diagnosing commercial vehicle issues can
be challenging and stressful, especially when
you run into a laundry list of fault codes while
plugging in an engine control module (ECM).
Deciphering which codes are relevant can
become overwhelming in the moment.
When I was first learning how to diagnose,
I was taught the KISS (Keep It Simple,
Stupid) method. That was tough to grasp in
the beginning because diagnosing a sophisticated
Class 8 truck is far from simple. During
early attempts, my eyes would glaze over, my
head would empty, and by the end of the day,
my body would feel numb. There were times
when I went in the wrong direction, and possibly
in a circle a few times. Hours or days later,
I would find the answer.
26 Fleet Maintenance | July 2023
with a higher degree of priority. Inactive
fault codes should be part of your diagnostics
through your process of elimination, but inactive
codes might not meet a threshold in that
current moment, such as with key on/engine
off tests or if a vehicle has an intermittent
concern. Even at times when the engine is
running, you may still need to meet thresholds
before that system code comes forward.
Once you read all the code descriptions,
it's now time to separate the descriptions by
their systems. For example, you may get EGR,
DPF, and SCR codes in one scan. I would then
group the system codes separately.
I find it less overwhelming to look at each
system group of codes individually. However,
keep in mind that the different system groups
may be related through symptoms within the
systems and may not show through a code.
For example, if an air compressor intake
hose ruptures and goes unnoticed for an
extended period, resulting symptoms would
eventually lead to EGR system concerns in
the form of a plugged mixer duct and EGR
cooler. Then the DPF and the diesel oxidation
catalyst (DOC), which are downstream
components, can be adversely affected. Low
intake pressure can cause excessive black
smoke, plugging exhaust filters and leading
to excessive or incomplete regenerations.
You should note that each OEM does have
a fault code ranker in development to help
point you in the right direction. However, let's
focus on how to find the best diagnostic path
assuming that we lack a current OEM fault
code ranker. When we have all our systems
separated and our repair history, code history,
and driver concerns reviewed, we are
ready to find our diagnostic paths.
While this process is still very complex and
technical, it can be simplified. The most logical
way I form my diagnostic paths is by using
failure mode identifiers (FMIs). Rather than

july2023

Table of Contents for the Digital Edition of july2023

Hitched Up – Using AI without losing what's important to your business
Equipment – AEB adoption speeds ahead
In The Bay – Bright ideas to speed up lighting and electrical repairs
Shop Operations – Battle of the bulging budget
Lubrication – Greasing: Manual or auto?
APUS – APU innovations take heat off fleets
Diagnostics – Don't distress; de-stress your diagnostic process
Technology & Maintenance Council Annual Meeting & Skills Contest
Fleet Parts & Components
Tools & Equipment
Product Spotlight: Wheels and brakes
july2023 - 1
july2023 - 2
july2023 - 3
july2023 - 4
july2023 - 5
july2023 - Hitched Up – Using AI without losing what's important to your business
july2023 - 7
july2023 - Equipment – AEB adoption speeds ahead
july2023 - 9
july2023 - 10
july2023 - 11
july2023 - In The Bay – Bright ideas to speed up lighting and electrical repairs
july2023 - 13
july2023 - 14
july2023 - 15
july2023 - 16
july2023 - 17
july2023 - Shop Operations – Battle of the bulging budget
july2023 - 19
july2023 - 20
july2023 - 21
july2023 - Lubrication – Greasing: Manual or auto?
july2023 - 23
july2023 - APUS – APU innovations take heat off fleets
july2023 - 25
july2023 - Diagnostics – Don't distress; de-stress your diagnostic process
july2023 - 27
july2023 - Technology & Maintenance Council Annual Meeting & Skills Contest
july2023 - 29
july2023 - 30
july2023 - 31
july2023 - 32
july2023 - 33
july2023 - 34
july2023 - 35
july2023 - 36
july2023 - 37
july2023 - Fleet Parts & Components
july2023 - 39
july2023 - Tools & Equipment
july2023 - 41
july2023 - Product Spotlight: Wheels and brakes
july2023 - 43
july2023 - 44
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