Hard learned lessons

Chris Diagnostician Commack, New York Posted   Latest   Edited  

We all get our butt handed to ourselves from time to time. For some of us, like me, it happens more than we like to admit. This isn't always a bad thing. We can use these horrible, horrible experiences as a learning opportunity. Most times, these failures can be our greatest teachers.

Early in my diagnostic career, I was working on a crank/no start on a Wrangler. I took the vehicle over from my fellow tech who got in over his head. I questioned him on what he did and where he was in the diagnosis. He said he checked powers, grounds, fuses, and a visual on the wiring. This was a long time ago and I do not remember all the specifics. I do however remember that the pcm was not turning on the coil. 

I determined that this truck needed a new pcm. I called the dealer, bought one and had it bench programmed. Installed the computer, and nothing. Same symptom. I got that horrible feeling in my stomach when a misdiagnosis happens. 

I decided to start from scratch. One of the first things I learned as a mechanic, was to check EVERY fuse when there was an issue. I pulled out my handy-dandy test light and got started. I immediately found a blown fuse. I replaced it and the truck fired right up!! I went over to the tech and said "I thought you told me you checked the fuses!!". He replied, "umm, sorry?"

I learned an expensive lesson at that point: Treat every vehicle as a new vehicle. Always start with the basics. I kept that pcm on the shelf where I could see it as a reminder. 

How about you? Which lessons did you learn the hard way? I'm looking forward to your stories.

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Bob Diagnostician
East Longmeadow, Massachusetts
Bob Default
 

Nope, don't know what you're talking about. Never happened to me..................... OK, just kidding, I've had my ass handed to me more than I would like to admit also. It's usually something really stupid simple that I missed because I was rushed and tried to shortcut things. One that I will always remember from years ago was a door diagnoses. It wouldn't open from the inside so I figured

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Martin Instructor
Burnaby, British Columbia
Martin Default
 

Don't feel too bad Bob. One day at the dealership some years ago, I was asked to fix the non-functioning DRL lamps on a white Chevy Impala parked out in the service driveway. So, I hopped in, drove it into the shop and started checking the lights, but found nothing wrong. That was about the same time the service writer arrived to tell me I'd got the wrong car. Another SA had moved the car I

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Chris Diagnostician
Commack, New York
Chris Default
 

That’s the best way to learn all about child locks!

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Martin Instructor
Burnaby, British Columbia
Martin Default
   

Okay Chris. I'll "bite" and "play". I'd like to say that "In the past 50 years I've never screwed up." Yeah, I'd like to say it, but that would be total BS. If there are any technicians out there claiming to never having had a FUBAR, either in a repair procedure or a diagnosis, then then haven't done anything! I'll start off with a couple of mine from the 1970s. It's funny how we can recall

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John Technician
Morgantown, West Virginia
John Default
 

I had a 2008 Chevy express van land in my bay last week from a fellow tech in my shop. Complaint was a crank no start, and a fuel pump relay control DTC. Tech before me replaced the fuel pump as he had no fuel pressure. So I go through checked the fuse for the pump, key on it had 3v. Okay that’s strange. The fuse is after the relay in the circuit. So I pull the relay out, still 3v at the fuse. I

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Andrew Technician
De Motte, Indiana
Andrew Default
 

Had a G-van that would run on the rack but not on all 4 wheels because of this one time... took me a while to figure it out. Ground from engine to frame was bad, somehow it would pull just enough when on the rack and start. I have noticed this on many others since.

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Martin Instructor
Burnaby, British Columbia
Martin Default
 

Speaking of the rack making a difference Andrew. I was doing NVH course with the PicoScope with my class using an '07 Silverado two years ago and again last year, All was fine for the first 7 pairs of students in both classes doing the run ups and when the 8th pair of students ran the truck up to the worst vibration amplitude, the PRNDL and VSS dropped out. They did all sorts of diagnostics by

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Pj Technician
Pleasant Hills, Pennsylvania
Pj Default
 

I had this exact thing happen to me, on this exact vehicle. I seen about 6 volts at the fuse, so I thought I was losing 6 volts from corrosion. What I didn't realize was there was 6 volts running through the body of the vehicle (where I had my multi meter grounded) and 12 volts at the fuse. But with how multi meters work, it was displaying 6 volts. I for sure learned about testing my grounds

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Andrew Technician
De Motte, Indiana
Andrew Default
 

Early 2000's Saturn L300. Had the 3.0 motor in it. Came in for a t-belt. I somehow forgot to lock the tensioner and took it on a nice long test drive. On my way back to shop it jumped time. Bent every valve. Send heads out have it repaired, then I learn about head gaskets. They are different side to side, somehow I flipped them around. Car ran for about 45 seconds then.... I break the cam

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Andrew Technician
Commack, New York
Andrew Default
 

I had a similar experience - I was working on a very old Land Rover and the customer was determined to drive it across the country to California but it had a no-start problem. I think I couldn't talk to the ECM. I checked everything twice and I couldn't find the ignition on power feed. The windshield had been resealed and water had leaked into the car. The customer wanted to drive the thing out

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Sean Technician
Cincinnati, Ohio
Sean Default
 

I also learned early on to treat every car as no one has looked at it, customer said they had checked all fuses all on and passenger window still inop went down now stuck, me being all gung ho rip the door panel off motor works fine. Switch inop, go to master switch to be sure notice the window lock was on.

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Greg Manager
Wilmington, Delaware
Greg Default
 

As a tech for …'s Auto Care i have abandoned the test light a use a meter and halogen bulb for testing and loading circuits. We just had a 2008 Cobalt with a no crank, no security light, multiple codes in the theft deterrent module etc. I was bouncing back and forth while working on another car and helping a fellow tech on it. this originally had an auto start installed and was removed

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