Logical troubleshooting methods

arctictraveller · 08-21-2021, 01:42 PM

Sometimes the only option you have to troubleshoot a problem is to make an educated guess and then throw parts at it in hopes you guess correctly. Lots of shops use these methods, but there is a better way. Accurate, logical diagnosis requires proper test equipment and knowledge. For the geeks among us, ATS has produced a bunch of excellent videos that will help you to better understand logical troubleshooting methods and test equipment usage. There is a lot of highly technical information in some videos, but others like finding the source of various leaks are pretty simple. Check out their list of videos

https://www.automotivetestsolutions.com/all-ats-videos

86Scotty · 08-22-2021, 06:53 AM

Man, this is great stuff! Thanks for sharing. I love his back-to-basics explanations.

1der · 08-22-2021, 09:29 AM

Wow, watched the 7.3 and the e250 4.6L videos. That is some incredible stuff and Bernie is just amazing. I would now love to know if a shop has the ATS or equivalent diagnostic system AND a competent operator to interpret the data!

Thxs! Great resource!

bigriver · 08-22-2021, 10:33 AM

Right... havin and knowin are two very different things. A good reminder when we might assume one means the other.

arctictraveller · 08-22-2021, 02:08 PM

Quote:

Originally Posted by 1der

I would now love to know if a shop has the ATS or equivalent diagnostic system AND a competent operator to interpret the data!

Thxs! Great resource!

I wondered the same thing, but I'll bet that if you called them up and asked for a list of their customers in your area, you could find someone with the tools and knowledge to diagnose your issues.

posplayr · 08-22-2021, 03:10 PM

I just watched part of one of the videos. Clearly, this AST tech has years of experience and has internalized a model of the engine/controls based on the available OBDII data.

So he is using that internalized model to deduce potential faults based on the measurements, then he is exercising the part of the engine operating regime that the suspect faulty is occurring to further expose the problem symptoms.

He is in the process of drilling down to the most likely component mis behavior that matches the data and then will probably change out that part following a detailed diagnosis. If he finds it fine, if not he starts over looking for an alternate fault possibility.

I'm not sure that I would characterize this as "logical troubleshooting" as much as it is "model-based" troubleshooting. Not saying it is illogical just much more sophisticated than pure deduction. This is certainly way beyond the typical troubleshooting guides I see in FSMs.

BCam · 08-22-2021, 05:32 PM

Is there a search function for the videos or do you just have to page through them to find applicable videos?

arctictraveller · 08-22-2021, 07:21 PM

Quote:

Originally Posted by posplayr

He is in the process of drilling down to the most likely component mis behavior that matches the data and then will probably change out that part following a detailed diagnosis. If he finds it fine, if not he starts over looking for an alternate fault possibility..

No disagreement here. The point I am trying to make is that he is using data, rather than anecdotal evidence to make a diagnosis. Pretty much every day I read pleas for help in fixing a problem on different forums, but there is little information from which to make helpful suggestions. Simple tools like volt meters, pressure gauges and amp meters help tremendously. Lots of folks, through no fault of their own don't have the skills or knowledge needed to effectively troubleshoot, and instead just start replacing parts that other folks have suggested. Sadly, even professional shops often times use the shotgun method and just start replacing suspect parts, all the while charging the client and not fixing the problem. This was made clear in the first video I watched where a shop had replaced several expensive parts without fixing the issue. I guess the point I'm trying to make is that learning a few basic skills like the use of a meter can help solve many problems, far better than just guessing that the battery is bad, when really it was the alternator.

posplayr · 08-22-2021, 08:31 PM

Quote:

Originally Posted by arctictraveller

No disagreement here. The point I am trying to make is that he is using data, rather than anecdotal evidence to make a diagnosis. Pretty much every day I read pleas for help in fixing a problem on different forums, but there is little information from which to make helpful suggestions. Simple tools like volt meters, pressure gauges and amp meters help tremendously. Lots of folks, through no fault of their own don't have the skills or knowledge needed to effectively troubleshoot, and instead just start replacing parts that other folks have suggested. Sadly, even professional shops often times use the shotgun method and just start replacing suspect parts, all the while charging the client and not fixing the problem. This was made clear in the first video I watched where a shop had replaced several expensive parts without fixing the issue. I guess the point I'm trying to make is that learning a few basic skills like the use of a meter can help solve many problems, far better than just guessing that the battery is bad, when really it was the alternator.

I don't disagree, I just got the sense that anybody that doesn't understand troubleshooting would quickly become overwhelmed with what that tech was doing. He is not just measuring volts and amps he has an entire array of engine parameters that he is working through various scenarios of what seems to work and what is wonky.

This requires a model of the engine that he has internalized. He probably doesn't really even understand in a formal sense what he is actually doing.
This is very true for a lot of professionals. They just have learned to do it and it might be overwhelming. Diagnosis and fault isolation is not a generally easy task although there can be simple problems to isolate.

Fault codes are supposed to provide a basic automatic trouble shooting capability. More advanced diagnosis algorithms are going to be doing what he is doing. Understanding fault codes and how to check and clear them is going to be the basics. What he is doing is advanced. That is my only point.

arctictraveller · 08-23-2021, 11:37 AM

Quote:

Originally Posted by posplayr

I don't disagree, I just got the sense that anybody that doesn't understand troubleshooting would quickly become overwhelmed with what that tech was doing.

He probably doesn't really even understand in a formal sense what he is actually doing.

What he is doing is advanced. That is my only point.

As I mentioned in my first post, there is a lot of highly technical information there mostly suitable for the geeks among us. I spent a large part of my life diagnosing and repairing CNC machinery and controls, and a lot of what I saw in the video was beyond my current understanding, but it was still valuable to me. I do find you comment "He probably doesn't really even understand in a formal sense what he is actually doing." rather interesting. He has a better understanding than most professional mechanics.