I think the Art of Diagnosis is something you learn over time. Some people have a natural ability, but I think they still need time and experience to develop…
The Art of Diagnosis -ETCG1
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“i went to go to work one morning and my vehicle would not start! whats
wrong with my car?” i always tell those customers ” i left my crystal ball
at home today” over the years i have created different flow charts for my
diag for different scenarios such as crank/no start, no crank/no start,
ect. you nailed it on the head etcg. in my opinion diagnosis is my
favorite part of my job. probably because i get paid hourly and not flat
rate, lol, and it stimulates my brain. its not the same old boring front
end work, services, ect. i like to treat my diag’s such as crime scenes.
i also never make assumptions, because that will stray me away from the
basics, and the obvious. i agree it is an art. anyways thanks for the
videos, much appreciated. you, and im sure your work remind me why im in
this game.
I will make this comment (a long comment): Not all engineers ignore ease of
maintenance and real word data… I’m an Electrical Engineering Technology
Student (Senior in the fall) and more times than one would expect, real
world “results” dictate designs.
Example: electronically tuned radios. All modern radios are effectively
tuned by a voltage input (the device is called a VCO if you’re curious).
However, the voltage to frequency (what determines the “channel” of what
the radio is receiving) ratio is not linear; a look at an old radio with a
mechanical needle/dial display will show the spacing between increments is
not even. While one could run a bunch of statistical math to find an
approximate formula for this ratio (and I’m sure somebody out there has
programmed a radio that way), what usually happens (like in an FM radio I
made for a project this winter) is that for every possible (or practical)
frequency, a voltage is found and these two are in a lookup table (my radio
had 100 entries). While this sounds (and in a way, is) crude, and can be
tedious to create (manually dialing in 100 entries a few times over isn’t
fun) it’s what works best.
Good engineering isn’t about mathematical perfection or theoretical
prowess; it’s about making a design that does its job in the “best” way
possible. In the case of a car, being maintainable and built decently to
the price point is part of that (at least in my opinion). Granted, there is
an argument to be made for increased part sales or increased dealer repair
revenue, but quality sells cars, not money pits. Slapping out a crap design
may sells some parts and repairs in the short run, but in the long run,
repeat customers at the showroom are what keep an automaker in business. To
me, as an engineer of the near future, there is no excuse to spit out some
theoretical barely tested (actual testing) as a final design and leave the
actual testing to the consumers… Automakers doing such (especially on
issues that have been around for multiple years) is bad engineering and to
me, unacceptable.
(kudos if you read this far)
Experience can also be a trap. After you’ve done diagnostic work for a few
years, you begin to simplify, based on what you’ve seen. So, if you’ve seen
ten cars of the same year with the same problem, the eleventh car will be
diagnosed in your mind as it is rolling into the shop. Then you get a rude
surprise, and it’s time to exorcise the pattern recognition demons and
exercise some fundamental diagnostics. Interestingly, the guys just out of
school are more practiced at going back to fundamentals than are those
who’ve been working for years.
I have a rule, If you do not know how the system works, you cant fix it. I
agree with everything you brought up in this video. Excellent.
I once had the same problem on my ’68 Galaxie — no brake lights. Of
course it’s the brake-light switch! Replaced it… Didn’t fix the
problem. Say what?!! Turns out that ALL of the brake light-bulbs had
blown… At the same time… What are the odds of that happening?!
Moral of the story? No matter what the evidence you *think* you have, go
through the proper diagnostic procedures anyway. I should’ve checked to
see if I was getting 12V at the back when the brake-pedal was depressed —
or at least I should’ve checked the bulbs to see if they were good or bad.
But I skipped that step and immediately assumed the switch was bad. Spent
time and money replacing a switch that was perfectly good, because I didn’t
spend an extra 5 minutes on diagnosis. *Lesson learned*
Are you any good at diagnostic work? If so, what’s your secret? The Art of
Diagnosis -ETCG1
Everyone thinks differently so there is no right or wrong way .when things
get tough I like to test and eliminate parts if possible , because
everything that you can prove good is no longer a suspect, and .when
checking a part remember to ,ask yourself What does it take and How does
it work ,what inputs or outputs is required to make it work properly ,and
is it dependent on other parts to work. and never overlook the obvious.
Really it is hard to summarize how to diagnose ,there are basic steps but
each situation is different.
You learn as you turn. Don’t be lazy, dig in there, & get your hands dirty.
Also if your having trouble deciding witch of the 2 parts to replace,
replace the cheaper 1.
You use to be straight foward and no nonsense….30% good
Diagnosis can be a simple process, or it can be a bitch, especially on cars
with OBD1 as OBD1 doesn’t always provide useful information. For example.
I’m experiencing an intermittent miss when idling on my 1994 Toyota
Corolla. Could be a lot of things, but the trouble code of 12 is virtually
useless: Plugs, plug wires, rotor, coil pack, distributor, or–god
forbid–intake gasket. Experience with this particular car and/or that
particular problem would be a god-send but, lacking that, my only option is
to start throwing money at it. Very discouraging.
“My car broke. What’s wrong?” – “Well, it’s broken, isn’t that obvious?”
;-)
i had the shifter stick on me once in the drive through. turned out the
plug came loose off of the servo
I feel like this video was made for me. I’m somewhat decent at replacing
parts, but I’m terrible at diagnosis. I recently posted a question to your
forum about my 87 MR2 that idles fine but nearly dies when you open the
throttle. My first thought was catalytic converter so I removed it but it
still does it. Also checked for vacuum leaks and found none. Throttle body
is clean inside, as is the air filter and PCV. Being a novice at diagnosis
I’m running out of things I can think of to check. Also there are no lights
on the dashboard and it’s OBDI so next to useless.
Sometimes diagnosis is easy, and other times it’s seemingly impossible.
good video , I had very recently a ABS Fault light appear on my cars system
check system , had it scanned , no DTS faults , turned out to be a loose
battery terminal , so the first thing the cars computer thinks is ABS
fault, easy fix , but something to check if it happens to you .
I love this topic, great video Eric! Starting out working on cars I
struggled the most with this (and still do). I always wanted to have the
answer right off the bat. You simply cannot do it like that. After years of
experience, I have learned to take my time, look for the “clues” and do the
tests. I do not have the level of automotive experience/education I want,
but I do not think I ever will because there will always be new things to
learn. Stay dirty and stay learning!
Real fixes real fast. Good video Eric I recently had a problem with my jeep
2002 throwing a lean code yup o2 bank 2 was reading lean but the long term
fuel trim was maxed out so the ecu commanded more fuel conclusion bad o2
yes I checked fuel pressure m.a.p. and checked for vacuum leaks none
present. Side note it ran better with the o2 disconnected
Just one thing, if you can’t get the shifter out of park, turn the key to
the first position to unlock the wheel. Then, move the shifter to neutral
and start the car.
Complaint, Cause, Correct….There really is no excuse for misdiagnosis
nowadays, especially with the awesome wiring diagrams and TSBs that are
available.
*sigh* Diagnosis is still very hard for me even though I went through auto
school and have been working as a Tech for 2 years. You really need a very
good understanding of the car and sharp mind for problem solving. I have
fair understanding on most of the cars, but still zero on that problem
solving mentality.
I love diagnostics. Started out by watching most of ScannerDanner s videos.
Then got myself into a position at work to get all the CEL and diag work.
I use the scientific process every time. You have to be honest with
yourself. Its OK if the data doesn’t support your hypothesis. Always follow
the data.
The key for me is I want to see the part broken. I want to have a
measurement that 100% shows the problem. Like smoke testing an intake to
find the cause of a lean idle. If I don’t see smoke then I have to try
something else.
Anyway, system knowledge will come as you have more experience. And
understanding current and voltage and coils and motors and magnetic fields
are critical to this.
great video eric.diagnosis for me always starts with confirming customer
complaint.after that,depending upon complaint is usually a good visual
inspection.check for tsb,s-that is very important
First off Eric I do enjoy watching your videos. As an automotive technician
at a Ford dealer myself, I can relate to your experiences in many ways. I
have been doing this for 4 years now as a fully certified senior master
tech working on the line and I do understand the art of diagnosis as well
as the price and value behind an accurate one.
However I will say that forums like the one that you have, really any
automotive forums in general cause nothing but issues in the eyes of the
professional technician especially a dealer technician working on a single
manufacturer’s vehicle line. I say this because for the most part, I know
my Fords. My salary reflects on that as well as my tool collection and
prior training recognition.
If for whatever reason I don’t understand a particular system, I have
access to the manufacturer’s work shop manual, scan tool and TSB’s and or
SSM’s. If further action is needed in a particular scenario, I have a
hotline and field service engineers at my disposal if necessary. Basically
I do not have a need for a forum as a Ford automotive service technician
because of the above information I listed that I am provided with on a
daily basis.
My problem that I have seen first hand in this industry is when customers
come in proclaiming that someone on a forum told them that the issue with
their vehicle is “X”. The arguments and de-evaluation of my diagnosis will
then soon start to ensue as a result of these forums. Sometimes this is
resolved and the customer will come to grips with the fact that their trust
needs to be with the person standing in front of them, representing a fully
operational dealership level repair facility, rather than the guy
they listened to on the internet sitting behind their computer.
Other times the customer will leave and make an attempt themselves or being
it to “their mechanic”. Many many times it will end up back in my hands,
now with the customer paying more because of the extra time needed on my
end to rectify and issues someone else caused.
The internet is a big place that is, on the optimistic side, a great place
for information! However some if not most is garbage and misleading,
becoming troublesome for the technician that sees these things every day. A
guy I used to work with said it best in my opinion, “Anyone who shares
knowledge that has potential to be profitable for themselves, for free, is
someone who is misleading, egotistical and stupid.”
Practice -> Experience -> Wisdom. No easy shortcut :)
I would say listen to everyone, gather all the data/documentation you can,
but trust nothing without verifying it for yourself. Too often other people
will send you off on a tangent. When presented with a difficult problem by
nature we seek help from others even if only to confirm our suspicions.
While good information is out there by the ton, there are also those land
mines of bad diagnosis methods that are just waiting to ruin your day.
First of all I want to thank you for all the time and effort you put into
your channel. Ive learned alot these past 2 years I been watching you and
Paul Danner put nothing but gold in regards to how much money I saved and
made fixing cars. Thank you God Bless
Story time. So I bought a 97 Escort Wagon for my sister from a friend.
It’s in decent shape and was well taken care of. But shortly after we
bought it the ‘hatch open’ light on the dash would blink on over bumps. I
chalked it up to being the switch failing in the jam. Fast forward a few
weeks and my sister calls me saying she can’t get the car out of park. I
ask her if she had brake lights – she states that the hatch 3rd brake light
works, but the main ones did not. So I replaced the fuse and the bulbs
finding that one bulb had blown. This worked for a bit. Then it happened
again. So I started tracing wires. Come to find out the wiring going from
the hatch to the body of the car had cracked and was shorting out on the
car’s body. Low and behold, after some solder and replacement wire, the
problem never came up again.
This experience basically taught me how to go about basic diagnostics. In
many cases however, you also may have a ‘diagnostic’ mindset just by
default.
let the tech figure out the problem, dont come to me just wanting a part
replaced as it only wastes my time and your money because i will change the
part and it wont solve the problem then you will be pissed and i will
charge you anyway and give you the option of performing a diagnostic for a
additional $100
Just got done doing a diag, your video made me chuckle because this
customer did the exact things you were talking about. P0171 and P0174, both
banks lean on an Infinity I30. Customer replaced both upstream sensors.
Didn’t fix it so brought it to me. My first thought was vacuum leak, nope.
Hmmmm, looked at the data stream and the MAF wasn’t quite right. Aha!
Cleaned it and things got much better. Told the customer what was up, said
if the codes come back fairly soon it’s probably going to need a MAF.
Diagnostic work takes patience. When I started, the manual was my friend,
After a while of doing it, you start to see the pattern failures, and
common issues. My least favorite part is wire chasing. there,s a lot of
wire in some of those harnesses, so tracking a short can be quite tedious.
im not good with diagnosis, i have a blazer and i put a new air filter in
it, immediatly i got a code for a vaccum leak and i couldnt find it, my
mechanic found the problem wich was an improperly attached intake hose to
the throttle body
My goal in life is to become some sort of diagnostics technician. I love
doing diagnostics, it’s actually fun for me. Going through every part,
testing it, thinking of past experience to see what the problem might be,
and best of all, not screwing the customer. Instead of blindly swapping
parts for the cheapest possible replacement, like some poor mechanics tend
to do, I’d actually be figuring it out and replacing only what’s necessary.
The Art of Diagnosis requires a skill not often taught today. Critical
thinking. Ohh, understanding & comprehension are helpful also.
Seems to me like there needs to be more dialogue between engineers and
technicians, you should advocate this to the big car companies because no
one else seems to care.
My first car, which was also my previous car, was a 1995 Dodge Stratus. My
stepdad who was my main mechanic, and with over 30 years experience in the
field, told me that my car was an electrical and diagnostic nightmare.
Among many other things, that hunk of junk went through so many plugs and
wires. That was just one example.
What were you doing during night? Your eyes look tired.