Thinking Like an Automotive Diagnostic Technician

Thinking Like an Automotive Diagnostic Technician


hey everybody trusts for Hubble mechanic comm today we’re gonna be talking about using our brain to diagnose car problems so this is episode 62 of the humble mechanic podcast today we’re gonna be talking a little bit about the diagnostic process ways to think about how to diagnose cars the ways you can get stuck and then how to unstick that stuff so as a technician we all develop this diagnostic process now mine might be very different from yours which might be very different from the guy that works next to me but the end goal is always the same fix the car right the first time and do it as fast as possible and in my opinion they should all really start the same and that’s the most basic stuff duplicate the concern evaluate the entire situation of the car throughout this episode I’m going to be using the example of a lighting circuit because it’s so easy to understand and it used to be such a simple circuit which now is a lot more complex than that but it’s one that everybody can really understand there’s an old acronym k is s and that was keep it simple stupid I think a lot of places have kind of moved away from that because someone might get sad about being called stupid but that’s neither here nor there because it really does apply to fixing cars with vehicle systems that are so complex how do we even keep it simple you have modules controlling everything in the entire vehicle which is actually a good thing because it gives us a lot more information than we would have had 15 or 20 years ago but with that extra information it’s actually easier now to get twisted up in weird problems than it ever was before so we really need to have a good diagnostic process and like I said it can be totally different mine’s gonna definitely be different from yours you may start by grabbing the scan tool and checking for faults where I might start by checking the fuses neither one of them are necessarily wrong they both should lead us down the right path it’s all a matter of the roads that we take to get to the end result which is again fixing the car right the first time and doing it as fast as possible you know had an instructor named Dan years ago the Volkswagen Academy awesome dude and and everything was always work easy too hard and then he would ask questions like oxygen sensors easy to diagnose or hard to diagnose which it could really be either one and all pens but I really adopted that work easy too hard mentality I probably already had a lot of that before the training but it being ingrained in your brain the entire time you’re at training really does hit the point home and what I mean by work easy to heart is what are the things that I can do that are minimally evasive that require the least amount of work and they’re gonna give me the most information about what’s going on with the car I asked this question of every technician whenever they have a problem did you check the fuses and the answer is vary from yeah I checked them and they’re good no I didn’t I checked the one for the circuit or uh yes where I asked the question you don’t get to ask that question back cuz I don’t know basically asking me if they check the fuses which I don’t really understand but something as simple as checking fuses should be easy and then we work to hardware you know we’re taking the dash apart to trace wires or chase down a bad ground and I’ll say it because I have to say it every time I talk about checking fuses always always always one more time always check all the fuses don’t worry about the one for the circuit check them all if you got to get a test light or a Power Pro out check every one of them also don’t forget to make sure that they are all there and installed in their right locations see more than one pretty good technician kit their butt kicked by a fuse that was missing so remember check them all make sure there’s a fuse installed where there should be and make sure you’re checking it with the circuit on there’s no reason to check the headlight circuit with the key off we need to make sure that whatever we’re testing is going to be powered up also when we’re thinking about diagnosis we have to have an understanding of the circuit if we go in 100% blind we’re just gonna wind up chasing our tail on a problem now I don’t need to understand everything at like an engineering level I do need to understand the system so think about a light what do we need to make a light bulb light we need a power we need a ground we need a light bulb we need wiring and nowadays we really have modules that control all these things so you can probably add a signal into that as well but that signal may actually be just the ground or the power it all really depends on the circuit we need to know what the car wants does it want to turn the lights on does it want to dim the lights is it a pulse width modulated circuit where it’s not sending a full 12 volts to that light all the time which is actually how a lot of lights are lit nowadays and we also need to know what the car sees and that’s really gonna be like a driver input so is the headlight switch turned on or has the rain light sensor told the lights to turn on and we can monitor that a few different ways we can look at it with a scan tool or if we don’t have that we have to evaluate the situation as we see it so let’s say we don’t have our headlights that work when we turn the headlight switch on what happens do the taillights come on do the parking lights come on do the lights on the interior come on if the answer to all that is no now we know we may have a problem central to the switch or the module if all the lights come on but the headlights now we at least know okay the light switch part of it is working we know we have some kind of signal in we know we have some kind of signal out now we can start breaking these circuits up into smaller sections and going after each individual component so instead of trying to diagnose a whole big problem we need to break it up into different sections and diagnose the ones that have the problem not necessarily worry about the things that are functioning properly so when we don’t do things like work easy too hard and keep it simple we can really get ourselves stuck and getting stuck can happen really really fast like mind-blowing ly fast you’re working and you’re on the right track and all of a sudden you’re 7000 steps away from from being on the right path it usually comes in a few forms either we’ve assumed something is good that we don’t know or we’ve assumed something is bad and we don’t know and a lot of times that’s how incorrect parts get installed because we just assumed this was the problem instead of actually doing the testing to find out for sure we also skip basics because we get in this mindset of it can’t be that because it can’t be the headlight switch because all the other lights work it can’t be the fuse because the fuse that the wiring diagram says controls that circuit is good but you know and I know my fellow technicians will understand wiring diagrams are not not not 100% accurate I I have been burned by wiring diagrams not being right on multiple occasions and that my friends is incredibly frustrating we can also get stuck in a scan tool loop where let’s say we check for faults and there’s no fault but we can and a test plan or we start looking at values trying to see what the car is seeing and we just get stuck going round and round and round and round not really doing anything not executing any tasks just looking at values which we may not fully understand what we’re looking at and why and if you don’t understand what you’re looking at and why you’re looking at it you are definitely gonna be caught in that scan tool loop another thing we really have to consider when we’re dealing with a scan tool is we may be having this problem because the module itself is bad so let’s say we’re looking to see if say the body control module is turning that light on it says it is but it’s not actually doing it because the module is what the problem is so it’s so so easy to get just stuck and then once you start to get stuck if you don’t immediately get out of it your brain starts to do this tumble thing and you know you just wind up making it worse and worse and worse then you get frustrated and that’s usually about the time where someone comes up and asks you a really dumb question or you have to do some other tasks or you know you get pulled off the job for something else and and sort of lose your train of thought and this is where the only way to really solve these problems is with experience so what happens when we get stuck how do we how do we get ourselves out of that stuck out of that run out of that mindset of men’s cars kicking my butt I don’t know what to do I feel like I’ve done all this work I’ve checked all this stuff and I’m no better off than I was three hours ago first things first we need to stop I like to walk away for a few minutes and I think if I were a smoker I would go smoke a cigarette but I’m not so I don’t you know I like to I don’t know check my phone or check my emails or whatever just get my mind off that car even pulling another car in the shop and say doing an oil change it can sort of take your mind off this really intense problem and put it on this really easy task where you see a start you see it finish the cars done and you pull it out and then we come back and sort of refocus our brain on the car we’re working on I also like to generally get more information if I’m stuck and can’t figure out a problem it’s time to do something different it’s time to talk to the customer and see if there’s more information that they have that maybe they didn’t tell you right up front because a lot of customers don’t know I need to tell them all this extra information don’t let your customer tell you what you need to know get out of them all the information that you can everything about the situation and the failure that you can you need to get from the customer and then you can decide don’t need don’t need don’t need don’t need here’s the gem that’s gonna help me fix this car this exact situation actually happened to me a couple of days ago and it was the first car of the morning and I had a new guy start and it was the very first car that he ever seen come through the dealership so it was a really good example that I hope that he appreciates but my guess is that it probably sort of went right over his head I had a 2006 Beetle convertible come in with the convertible top not working a problem that I’ve seen time and time and time again my very first step was to see what it was doing i unlatch the top I pulled the button nothing okay now I got something to go off of but what I also notice is that when I unlatch the top the convertible top light flashed so now I know the closed position switch is working I get out my power probe I buzz down all the fuses all the fuses are good I relearned the pinch protection for the windows because that can actually cause the top not to work still nothing okay so I’ve done like three really easy things that have taken me all of maybe five minutes I’d go back to the trunk I’d release the pressure on the hydraulic pump and I roll the top back so I know mechanically it’s not sticking or stuck close the top now it’s time to get the scan tool get the scan tool no faults stored I go in and I check the values and I see that all the positions of the top are reading accordingly the top should close when it’s closed the top showed open when it was open top showed in the middle when it was in the middle and the car seen that I was pushing the button both open and closed now this is the point where it’s time to stop because my next step is going to be intrusive my next step is going to be taking say the rear panel out of the trunk and checking for power and ground at the motor so I stopped and went to my service advisor to ask the customer these few questions how long has it been doing it when’s the last time the top worked is there any other information that I need how often do you use the top that way I could get a little bit more information about the entire picture because all’s I know is the top doesn’t work but everything in the system seems to work other than actually the motor pulling the top back and putting the top forward so she talks to the customer customer says I’ve only owned the car for a few months the tops worked two or three times all of a sudden one day didn’t work but it was weird because I was in a few weeks ago for a headlight bulb and when I left there was a fuse on the floor okay that’s interesting because generally there’s not just fuses laying on the floorboard of your car the fuse on the floor was the Golden Nugget of information she had owned the car for a few months not too worried about that at this point the top had worked two or three times okay so we know she has used the top we know the customer knows how the system functions and how to use it and then at some point this has worked properly so now it’s time to address the fuse issue because generally fuses just aren’t laying on the floorboard of the car so I went back to the fuse panel to check and make sure that there was fuses in each location that there should be and everything was cool there so I went to the wiring diagram to look up any more fuses in the system lo and behold there was a fuse on the relay panel for the convertible top climb up under the dash take a look sure enough there was a fuse missing go back to get the right right amperage fuse information pop a fuse in it top works just fine so had I not gone to the customer and got that information I probably still would have got there but it wouldn’t have been so fast it wouldn’t have been a 20 minute diagnosis it would have been maybe an hour diagnosis maybe to who knows maybe I would have got sucked into that scan tool loop and just went round and round and round looking and checking and looking and checking and not really doing anything now some might say this is information the customer should have told me maybe some they say the adviser should have gotten this information maybe ultimately it’s up to the technician to get the information that they need to fix the car and at some point you just got to do something you got to try something different than you’ve been doing otherwise you’re just gonna be stuck and being stuck does not get cars fixed also when you get in that stuck mode it’s a good idea to sort of bounce something off the guy working next to you you know hey man have you ran into this recently or you ever run into this weird thing or hey check this out this is crazy have you ever seen it and that even if they don’t know the problem sometimes you talking about it and actually saying the words can help your brain process what’s going on and process a problem better it works really well for me and I know it works really well for the other to my shop to also if you have a good process and had been writing everything down throughout the entire diagnosis you can go back and read through your notes and go okay check this check this check this ah crap I never checked this one thing let me run and check it real quick it’ll take three minutes and lo and behold that may be the problem because you skipped a step but at least since you wrote everything down you can sort of backtrack that and find out where you skip the step so there you have it welcome inside the brain of a technicians diagnostic process you know it can be a little squirrely in there and and different people do things different ways but again our end goal is to fix the car right the first time and do it as fast as we can all right guys I’m gonna wrap it up there if you have any questions or comments post it in the comment section below hey if you liked the video throw it a thumbs up on YouTube you can also subscribe on youtube or on the blog at home with mechanic calm you can follow me on facebook twitter or instagram the blog volcanic calm and obviously on YouTube alright guys thanks for watching bringing gin-and-tonic out of a beer mode


Leave a Reply

Your email address will not be published. Required fields are marked *