How to Not Fry Your PCM- SBQM Channel Free Video Sample!

[@orionmyth]

We have no excuse not to step up our diagnostic abilities with this kind of (free) content 😎

[@labradormcgraw]

This guy is absolutely brilliant. No wonder he's so popular. You wouldn't get this level of tuition at college, let alone on any other KZbin channel. And this is one of his earlier videos - he's only gotten better since!

[@SchrodingersBox]

🙏🏼

[@MarzNet256]

Yes. He is incredible.

[@stephennichols586]

Been doing air-conditioning and refrigeration for 40 years and now I'm retired and I enjoy working on ars and just learning automobiles and diagnostic but I have always used the troubleshooting any electrical problem source ,path switch , load and sequence of operation to test electrical circuits and don't get overwhelmed with the electrical diagram or schematic ,just knowing what isn't working and only be concerned with that find the component and follow the path backwards to the voltage source .I have enjoyed your videos and I have learned in a few weeks of watching you and your explanation of the sensors and components the ecm and the pcm are controlling and that's what I am looking for thanks for sharing your knowledge and I am going to subscribe to your advanced learning channel. Looking forward to learning and sharing some of my experiences and helping younger students and future technicians

[@yoyo54314]

30 minutes extremely well expended. and I passed all the tests,. thanks to you of course.

[@SchrodingersBox]

Gotta love the negative commentors who wouldn't know how to diagnose a dead battery much less a TPS. Am I wrong or would only a fool thumbs down the source of knowledge that would finally make them competent?

[@themountainman2613]

I don't think a smart knot with a balljoint hammer would make them competent-- they know how to cross thread spark plugs. Most of us like to know how to diagnose and (repair). People like to hate what they don't know or understand. Your channel is extremely informative, thanks for taking your time to teach us!

[@SchrodingersBox]

Jeremiah johnson "People hate on what they don't know or understand" Words of wisdom there my friend- that is so true!!!

[@renewedautodiagnostics6525]

+Schrodingers Box I don't think the test done around the 14 minute mark is a good one because if the coil was shorted then you could draw more than 10 amps and blow the meter fuse, your thoughts?

[@schrodingersboxquantummeka2008]

+Nikolay Baranyuk Good point- you're right!

[@SchrodingersBox]

bidoubleo tiwhy Happy thanksgiving to you too my friend. And yes- the comments are gold on this channel. I also learned more from the comments than I have in 7 years of doing this hobby- by far!!

[@vusimuzizondo3623]

Just love this topic, it shows that you've to know and be patient when coming to electronic wire harness and their sensors and modules. Thank you Matt. Great work 😀👍🏽👏🏽

[@abubakarisadiqueibrahim481]

Your explanations goes down soo well. It's very easy to understand you than most of the videos i do watch. Thanks keep it up.

[@SchrodingersBox]

Glad you like them!

[@jasonjoncas5998]

Also very important have the the right size terminal to probe the terminal to not overspread it. And to test the drag on the terminal for a good tight contact. In my 30 years experience many problems are caused by other techs spreading the terminals causing additional problems .

[@SchrodingersBox]

In your 30 years experience you use a noid light set instead of just a test light???

[@guledmah5872]

The best teacher I have ever seen thanks for your efforts

[@chrisdaniels4674]

Thank you for the fuel trim diagnostic information. Really helped me understand something I knew nothing about. This guys a genius

[@emiliomunoz2037]

Thanks for the knowledge, it has improved me tremendously in the diagnostic side. Your a very good teacher.

[@tomaszradomski5411]

Great video Matt. At 19:36 you mention that it would be a good idea to use a fused jumper wire which I agree with because there is a small possibility that the underlying problem was an internal short in the injector. That in turn would blow the fuse on the wire supplying it with power thus matching the previous symptom of 0 V coming to the injector. But if we then supply the injector directly the jumper wire might carry enough amperage to blow the pcm. So it would be best to always use protection ;)

[@frankminakin1080]

Just found you on KZbin all I can say is simply amazing content also video length is perfect for my treadmill use every morning 👍🏻

[@SchrodingersBox]

Glad you enjoy it!

[@AllenNix-iz6ev]

Even if you know it's always good to watch someone else's way sometimes you will learn another way.... Good information thanks .

[@remotaurog]

Great video,your right about doing this stuff on cars,you can look at diagrams all day long but nothing beats the testing experience.

[@shiewaanwyeth5922]

You made my day sir. Your info is just what the doc ordered. Thx.

[@SchrodingersBox]

Thanks you made my day too!

[@charleswilson4598]

I am a retired electronics tech . I am no expert mechanic but I have repaired my cars since my 20's (now 82) and have reasonable mechanical skills. I have rebuilt a couple of engines, but there is a lot I can't do and a lot that I don't know. I drive a 1992 Ford F150 that has three relays. But I have been paying attention to the newer cars too, and have helped troubleshoot a couple of them. That taught me how much I don't know. Right now I am working on my grand daughters 2010 Cadillac srx. I had to get a new scanner and it shows a U0100. From the symptoms I believe the problem probably is a bad ecm, but I am checking the power and grounds to make sure it isn't something else. Anyway, bottom line is that I have decided that modern cars are really computer systems with an engine attached. I find the automotive electronics very interesting and want to learn more so here I am.

[@prosperandbehealthy]

*Thanks, great video. Like you said in the beginning of the video, if you don't know basic electrical, learn before you start testing. It seams the Auto industry purposely make many sensor's that eventually fail, but what you are saying is that you have to look at the whole picture because it can be different problems. For Example; I just changed my fan resistor and wire connector because my car was overheating. Yes, the resistor and connector wire was burnt, but the radiator was also clogged, and I had to change the radiator, but I had to go much further and change the thermostat and The cheap plastic housing. That finally solved the overheating problem. Thanks!* 😂😂😂

[@FreeKanal]

I have basic electrical knowledge, very basic(even though I'm the son of an electrical engineer :P ). Thanks to your videos, which I sometimes watch several times to understand and make this knowledge and understanding sink in, it is quite easy. Very clear explanations along with illustrations on the white board make it really friendly. Thanks again! I would just add a warning for other beginners who use any wires or test leads to be careful, when, for example, improperly leaving uninsulated wires, they do not accidentally short-circuit those that will cause damage, e.g. fry the PCM or start fire. Sometimes engine vibration/closing doors alone can cause contact and short circuiting. I wish You best and thank You again. We need more people who approach things like You do!

[@SchrodingersBox]

Thanks for the comment and yes- it takes most people several times watching before it sinks in. I am the same way!!!

[@armandofierro700]

I'm so happy that you were so nice to people who didn't understand why the paper clip was a bad idea, LOL.

[@lmstuber6044]

Brilliant brilliant video. I'm going to be joining your membership. Iv been a membership of mercanic mindset for about a month now .And watching pine hollow auto diagnostic and subscribed to you for a few years now IV learned a lot about the basics on this one.👍

[@SchrodingersBox]

Thank you! I guarantee you won’t be disappointed!!! It will be the best $3.49 you ever spent I guarantee.

[@stephenhowe5123]

Thankyou for the info.Reading other comments proves your correct that we all learn our own way to diagnose even when they do not know it and turn to negative remarks. Thanks again.

[@GripFreak]

This video is a great example for anyone considering joining the SQM community to go for it. This is a final video in a series on the SQM channel. The prior videos teaches you what he is summarizing in this video. Can't recommend the paid channel enough.

[@SchrodingersBox]

Thank you my friend!! Glad you finally got access!!

[@bradwettig3441]

Its amazing to me that anyone who owns a computer can't afford 4.50 a month (about 15 cents a day). Most people probably lose that much in spare change every month. There is nowhere else I could find this quality of information for this price. Keep the videos coming!

[@SchrodingersBox]

+brad wettig I like the math reference!! I easily lose 15 cents a day from my pocket digging my car keys out!

[@RADMAGE01]

+brad wettig For just 15c a day, you too can help freezing biologist-mechanics in Colorado warm their garages through all 9 months of winter.

[@SchrodingersBox]

John Ris Hahahaha OMG please dont send Sally Struthers over here- I don't nearly have enough food for her

[@joesno406]

Your The BOMB BRO!!!! (Some having a radiater fan not working situation ), I seen people use a paper clip to insert into the coolant temp sensor end that feeds power/signal to the coolant sensor to bypass the sensor to see if fan then works Is this a nono too?

[@TheWicklunds25]

I'm definitely better at the mechanical than the electrical but this crash course is worth its weight in gold.

[@ekimbrough1413]

Thanks Matt! This video was double GOLD! God Bless! Yes, please produce a video on Bi Directional Scan tool! I will be purchasing one in the very near future, and need the tutelage on how to properly use it! You have my thumbs up and subscription! 😃

[@SchrodingersBox]

Awesome, thank you!!

[@roundcornerent]

Matt, you and your videos are just fantastic man .

[@SchrodingersBox]

Wow, thanks!

[@siphomabhena4437]

Thanks for your videos, are much educational and I'm from South Africa

[@sabergermd]

Another great video on electrical diagnosis. It seems some people were really trying to get your goat below. I see you held your own but you do make it too easy. Trolls will be trolls. The issue with the use of a scope is not so much price but the steep learning curve involved in getting useful results. I recently bought a non-automotive Picoscope (2205A) and have been learning to use it for relative compression, secondary ignition wave forms, current ramps, etc. I have spent hours learning how to set up the software (Picoscope 6) and probes(amp clamp, induction, etc).

[@rulebraking]

Awwwwwsommm! Just what I needed not to fry my ECM- signing up for the subscription!

[@micheller8014]

A thumbs down does not mean it is bad content. Sometimes it is the way it is delivered.

[@SchrodingersBox]

Yes, there are some people who are too stupid to realize the content is all that matters

[@armandofierro700]

This guy at times can be bit of a smart ass but can you imagine the comments he has to read. On the other hand I learn everyday. This guy is great!!!!

[@SchrodingersBox]

Thanks- yes I do bite back in the comments lol!

[@Derabjee]

Looking forward to your videos on diagnostics with scope. I've been using the picoscope for a while. But it actually doesn't matter. Once you get the basics and realize what you're doing you can work with any scope.

[@jonathanrpu]

Enjoyed you and descriptions of other Knowalls but know little....Enjoyable series of videos...all the best and keep well. N.Ire. The U.K retired and love the show.

[@Gsxforsale]

For some reason you jumped onto my recommended videos and for that I am thankful. New subscriber.

[@SchrodingersBox]

Thanks for subbing

[@dade567]

Great stuff. I thank you for sharing your knowledge. I want to understand concepts and using critical thought in my work.

[@SchrodingersBox]

You are in the right place!!! So far i've only found 80,000 others like is in the whole world so we're not too common in this field!!

[@kamranjalalian4034]

Brilliant demonstrations, even though some people think you go over the top with the explanations! Of course having the right electric wiring diagram is a must. Any idea where your viewers can download the Ford wiring diagrams, preferably for free?Keep up the good work.

[@johnsippel983]

gotta love them ls engines! I just did an ls1 swap in my thirdgen Camaro one of the hardest things iv done wiring wise but I had to learn it all on my own witch made me much better at it, its so cool seeing you do exactly what I did when wiring my car up

[@topezful]

Application of fundamental understanding, I have learned alot from your videos , desperate to see complete series.

[@abdelsadinodio7841]

Just awesome and crisp explained. I definitely love your videos man!!!!!

[@TheWicklunds25]

YES more on basic electrical please...

[@SchrodingersBox]

Duly noted. My pay channel has LOTS on basic electrical diagnostic procedures. Very step-by-step. Still in process of development but will let you know when it's ready!

[@aminullahfaizy6154]

Thank you sir for all you do for us like you said we need some more video basic electronic diagnostics sir

[@persadramnath6945]

Very good explanation

[@trainer2018]

Matt good job. I have something I would like to add. When you were checking battery positive supply at the injector connector unplugged that test is not totally valid. That test is only telling you if you have a open circuit or not, you are reading static voltage. You have to load the circuit to see an actual representation of the voltage at that wire. So hooking up a test lamp or using a substitute load rated the same amperage the injector is would be a better test. Or use a Loadpro which is what I would use.

[@SchrodingersBox]

+busjockey1 I was not testing for voltage drop at that time but I do check voltage drop through amperage measurement later

[@trainer2018]

+Schrodingers Box Alright so you were just checking to see if you had static Voltage? Sorry that just threw me off because you said that was a valid test. For checking for a open circuit yes. I understand your process here but you might want to clarify the difference between a Static Voltage Test and a Loaded Voltage Test: Voltage Drop. Someone new to doing this type of work could get confused and in effect not do these measurements properly.

[@schrodingersboxquantummeka2008]

+busjockey1 Yes remember this video is part of a whole 4 part series where I talk about all this stuff. I also talk about static vs loaded voltages in my video on voltage drop on this channel.

[@trainer2018]

I figured you did it's just at that part in the video on how you did that test I think it would have been a good idea to clarify this difference between the static and Loaded Voltage. Not trying to be a pain at all it's just I want everyone to understand the difference between these two readings. Keep up the good work.

[@trainer2018]

I will check out your premium channel, looks interesting.

[@tomclark3592]

Matt I am going to subscribe to your pay site tomorrow. Loved this video!!!

[@SchrodingersBox]

Thank you!! You will love it I guarantee!!

[@mingovazquez704]

Thank you Master for share your knowledge with us, well explained 👍

[@musaalgheriany8917]

yes it was a very useful lesson for me thank you so much

[@shayrhussain9188]

Awesome explanation sir, I found this video related to my recent Honda Element issue. I replaced the TPS sensor and during calibration, I feel possibly I fried my ECM because when I used the volt meter I mistakenly connected the black lead to Battery + and the red lead to the signal wire or 5v wire accidentally or both together, I heard a sparking sound but I thought it can be a relay or fuse noise. Well, when I tried to start the car it was cranking but no start. The fuel pump stopped priming on the ignition key in position. The next day I noticed the immobilizer green key flashing in the inst. cluster along with Check Engine Light and oil pressure. Also, DLC or OBD2 connector showed a linking error earlier that was working perfectly. Because of the check engine light, I am still hopeful ECM is good but in some forums, I saw ECU can still be bad. Kindly guide me in light of your best experience for possible reasons and fix. I checked all the fuses and relays are good along with the power and grounds.

[@jimschiltz5343]

I really enjoy your videos, Matt. Good job!

[@NotizLp3]

Best video 👍🏽😱 great instructors! Great brake downs and examples!

[@giftofnile]

Thank You Scroding Box you have a great VEDIO class room instructions solid advise

[@thanoongiravi4892]

Please do make a video on how to use a scan tool. That would be helpful. Thanks

[@RADMAGE01]

FINE MATT.... FINE! I'll go do my free trial of your new channel. But, somewhere deep down I know this is going to be like taking the free hit from the heroin dealer. Pretty soon I'm gonna be pawning stolen sneakers for a SBQM fix. Damn you! Actually I have just been waiting for a nice long weekend to start the trial. So good job on the timely reminder.

[@schrodingersboxquantummeka2008]

+John Ris Hahahahaha all part of my master plan lol. Big difference between what I'm doing and a drug dealer though- I purposely target schools lol.

[@ScorpionRegent]

+John Ris Not a fair comparison. Heroin just makes you feel good, this stuff allows you to improve your life. If only all knowledge was that addictive. I know that SBQM is going to be a valid monthly expense for me. It will easily pay for itself.

[@TheMessiah91]

Thank you for the information.

[@John-rz6sp]

Great video. Happy Thanksgiving to you and your family also.

[@SchrodingersBox]

+John B. Kobberstad Thanks John, same to you and your family!

[@SouthMainAuto]

Why unplug an injector when testing them at all when you own a graphing multi meter and a low clamp probe? IMO a test light a scope or graphing meter like a vantage and a low amp probe you can test all PCM circuits completely safely. In my whole life as a mechanic I have never seen a test light ever damage a PCM, ever. I think it is more of an urban myth of mechanics.

[@bbkmm1]

+South Main Auto Repair His target audience do not have Vantage Pro nor a low amp probe. Do it yourselfers don't have expensive diagnostic tools or it defeats the purpose of saving money. I do agree with your and Ivan's point of view on scope on a rope.

[@SouthMainAuto]

Well I am just thinking with it being an advanced diagnostic channel and given the price of scopes and graphing meters now days it would only make sense. I just bought a 2 channel USB scope that for less than $100 ya know. There are some really good deals on some good used stuff too.

[@bbkmm1]

Please let me know what kind USB scope and how you like it. I've been contemplating an economical way to get a scanner/oscilloscope. A used SnapOn Modis looked promising. However, the update cost, and your experience with your Verus gave me second thoughts. It looks like a AutoEnginuity and PC based oscilloscope is the best way.

[@SteveRobReviews]

+Qiong Jia hi I have the autoenginuity and I would not recommend it unless your a diy'er or don't want to spend more for pro level scanner. I find the PC scan tools like mine are very buggy and just wig out at times. Bi directional , not many functions. Hard decision , just depends on your budget . Hope this helps , just my experience others might have a different opinion .

[@bbkmm1]

Steve, what do you recommend? New Maxisys or used Verus/Modis? I understand Autel is being sued by some Manufacturers. It has more features, most are hacked. Since it is a Chinese company.

[@Viper81766]

Your videos are excellent and you have one bad ass Pontiac .

[@SchrodingersBox]

No argument here lol! Thanks!!

[@Pablo_Automotive]

Hi Matt. very good tips. =) When you measure this type a measure i recomend use the Multimeter VRMS es more exact because the multimeter VRMS cant measure voltage out 50Hz. But if you have a osciloscope not is necesary. A big Hello from Spain.

[@elbertmarks5799]

Outstanding.

[@timgroleau1612]

Well done.

[@mtrltoolman]

great video , priceless lesson thanks matt .

[@davidm3210]

Very special stuff, thanks.

[@SchrodingersBox]

Glad you enjoyed it!

[@davidostring7627]

Thank you for posting this video. It was really helpful.

[@stephenfiglewicz2317]

very educational. thank you.

[@ozzstars_cars]

Makes sense to me, good diagnostics

[@ΓΙΩΡΓΟΣΓΑΛΑΙΟΣ-λ9θ]

Thanks for your wonderful videos I would like to ask you as a beginner in which order we should see your videos

[@SchrodingersBox]

As a beginner you should probably join my pay channel www.schrodingersboxqm.com

[@arthurlull8681]

Thank-U-matt&UR-VEWERS💥💫

[@SchrodingersBox]

Yes the viewers are the ones who make it all possible!!!

[@anyheck]

For the last test, a moderate quality DMM (not the $5 harbor freight) will have a 10A fuse for the amperage scale, although they are much more expensive and hard to find than an automotive blade fuse. He really only needs a fused jumper if he is using a clamp ammeter.

[@hooverphonique]

Hi, a few comments regarding the injector tests... assuming the fuse is correct, it should be rated to protect the pcm against a shorted injector solenoid, so the first 2 tests shouldn't fry the pcm (I'm not saying that you should do them, of course, because they don't really prove anything).. The test where you bypass the fuse could be dangerous, on the other hand, in case the injector solenoid is in fact shorted... I really like your material, and actually this is the first time, where I thought - ehhh, that is not completely right... keep up the good work :-)

[@SchrodingersBox]

+hooverphonique I can most definitely, 100% assure you that you you are incorrect and you CAN and WILL fry the PCM by bypassing the injector. I have seen multiple times where a shorted injector has fried a PCM.

[@hooverphonique]

+Schrodingers Box so you're saying that the fuse does *not* blow in case you short the injector? why is it there then? just in case the insulation on the harness is compromised? And if you're so sure it will fry the pcm, I don't understand why you tell people that they can just bypass the fuse to check if something is wrong with the 12V feed..

[@SchrodingersBox]

hooverphonique Correct- on a PCM circuit with no current restriction the driver will fry long, long before the fuse. Remember on 12V Circuits they are virtually always ground side switched, so obviously fuses are irrelevant to protecting the PCM. I have no idea what you're talking about when you say i recommend to bypass the fuse to check a 12V feed- where did I say that?

[@TheSydwell]

Your comment "so obviously fuses are irrelevant to protecting the PCM." is problematic. Fuses are important! The first test to be performed should be to check that the sensor is not internally shorted to ground.

[@stephennichols586]

Use a light bulb to simulate the load

[@rens1489]

not bad at all! i would of thought putting jumper wires with the plug undone to sig/ground and the power feed from battery straight to the 12v pin, bit more mucking around though

[@patrickmoran6004]

You do do some brilliant videos. Could you do one on why I do not get a battery dashboard light when my ignition is turned on. The alternator is charging the battery at 14 volts.? Any ideas?

[@SchrodingersBox]

There is a wire from the alternator to the dashboard- either its disconnected from the alternator, its broken on the way to the dashboard, its disconnected at the dashboard or there is a failure on the IP circuit board.

[@billseay6399]

Hey thanks Loving it big guy

[@kgkthebanjoman]

A typical ammeter is internally fused at 10 Amps at the 10 Amp setting. Since the power source is fused at 20 Amps, the 10 Amp internal ammeter fuse would be safe for the system -- the meter's internal fuse would be the most vulnerable component.

[@SchrodingersBox]

That is not correct!!!! Most PCM circuits operate on well under 1Amp. You absolutely don't want to use the ammeter for that reason on such circuits. Use a LED testlight which is 50mA load. Do not use the ammeter!

[@kgkthebanjoman]

@@SchrodingersBox I see that I was not specific on which part of the video I was commenting on which led to some misunderstanding. I was referring to the MAF sensor portion of the video which was at about 28 minutes into the video where the 12 Volts was injected through the ammeter into the MAF sensor connector at the pink wire (the pink wire source was fused at 20A and typical ammeters are fused at 10A). This was not referring to the fuel injector and its connection to the PCM module portion at the beginning of the video. For the fuel injector portion of the video, an oscilloscope would be ideal for monitoring the voltage pulses at the switched ground (PCM) side of the fuel injector. I am not sure of how static sensitive these PCMs are but it might be a good idea to be grounded to avoid unwanted ESD (electrostatic discharge) while working with the PCM. Usually, being in contact with the chassis of the car is enough to discharge any damaging static. I would hope that the PCM modules are adequately externally and internally protected from ESD by design -- they probably are.

[@SchrodingersBox]

ah much clearer. yes in that case an ammeter is fine. I normally use an Amp clamp

[@JH-bh5lm]

Now that I have gone through this video about 10 times I have one question. The test no.6 looked very similar to the last test you did, except in the test no.6 when you tested the fuel injector you did not use a DVM in amps mode you simply just took the power directly from the battery. I understand that DVM in amps mode does not provide a load but I didn't see the reason for using DVM especially because you have a scan tool where you can clearly confirm the work of a MAF sensor. Is this assumption correct or am I missing something? Thank you

[@jamesbailey7785]

I have to admit I am struggling. Thanks for your help.

[@joeshearer1247]

You should say the dVOM in volts mode in more resistance rather than using the word load. When you said it was more load that sounds like more amps and less resistance to me. But then again I am used to higher AC voltage in the HVAC field so maybe it's valid.

[@joeshearer1247]

*is more resistance

[@SchrodingersBox]

+Joe Shearer True

[@joeshearer1247]

+Schrodingers Box thanks for the reply. You have a great channel. I'm a 2%er in my field too.

[@dancin4]

What scope/probe do think is the most useful? Are there any features to look for...I had a Heathkit!!!

[@schrodingersboxquantummeka2008]

+Dan Sisulak I have a video called "introduction to oscilloscope" that covers this

[@Riyad7]

Awesome. That's great

[@robmut1357]

Great video and very instructive. (I passed, by the way. Yay!) A minor question on the four cylinder remark at around 12:15: Why would the events happen faster? An injector on a four cylinder engine would fire at the same rate as a six or eight cylinder engine at the same RPM, correct? You get one fuel spritz per cylinder for every two crank revolutions on any four stroke engine. Only revving it up would make the events faster. Also, on an unrelated subject, is all that white cable sheathing stock or did you add it?

[@SchrodingersBox]

+Rob Mut True at the same RPM- I guess I was thinking how usually smaller engines rev faster but correct at Idle there would be no difference. The white wire sheathing was actually blue but it turned white within a few weeks because it was cheap crap lol.

[@billsigsbury4680]

@@SchrodingersBox That is Funny. I thought you used white because it was "cooler" than black reflecting heat away protecting Wires and Hoses from intense heat cycles! ;)

[@alrifainidal]

thank you for awesome explanation

[@marleythechameleonandherbi2724]

Top notch video. Very well done. Use of the word "load" a bit miss leading - I think use of the phrase "high resistance" fits better.. Thanks!

[@SchrodingersBox]

+B crinshaw Resistance is indeed the load when there is nothing else in the circuit restricting flow to do work.

[@marleythechameleonandherbi2724]

+Schrodingers Box - Right you are, it surely is a load - as a straight wire across an injector plug is a very, very good load - good enough to fry a PCM like you illustrate. Modern DVM's are a light enough load to keep drivers in the PCM safe. Very good videos! I'm a new subscriber and really appreciate your work. Thanks.

[@anthonysandyafful7526]

Great job, well done

[@joesno406]

Now if I praticed your current test (16:00) with black and red test leads switched But in same sequence Would I get same result? Not sure if I can remember sequence in test lead colors!!

[@elkarshofyelkarshofy1490]

Excellent

[@metalguru6152]

YES! YES! YES! I want to be in the 2% and it's possible althogh it is a bunch of work!

[@SchrodingersBox]

It is a bunch of work for sure. It took me YEARS to learn this stuff. YEARS!!

[@metalguru6152]

@@SchrodingersBox You are a great teacher! Your voltage drop vid is excellent. Also map sensor vid which I'm still dealing with on my '88 f150. I replaced brake booster &truck ran great until it didn't. I thought I had a bad throw out bearing b4, sorta sounds like that altho I recently put in a new clutchset (then the engine problems strarted lol) but now I think I'm just low on ATF for my M5OD 5 speed... I think excess drag of tranny is adding load to engine at start up causing the map code 22 ... not totally sure yet, but best to make sure tranny fluid is full b4 next step plus shift is bad now. I'll let you know what happens. Interesting to think that some ATF might cure the code 22!

[@metalguru6152]

@@SchrodingersBox yes, you knew it! The ATF wasn't going to fix the map sensor lol, but at least my tranny doesn't have a leak and it seems to be shifting better for now for some reason, it is an old cantankorous truck after all, anyway, yes, I have my work set out for me, Headaches but only cuz I'm trying to make this my daily driver but I'm fixing up this beatrer as a learning experience. I'll be watching more of you vids,learn to probe & get a scan tool, gotta figure out which one to get. Truck seems to run from cold w/out the engine light and it's running better than ever, compression's good (I replaced the injectors, 2 were bad which I learned not thru proper diagnosis but when I tried to clean them on the bench... I got a new saved 41 code, lean condition.. so I'm thinking vacuum leak, I'll hook up my $5 pickle jar smoke machine that I made... & check everything.

[@metalguru6152]

ok, to end the boring saga, a happy ending mind you, yes I am an idiot half the time but eventually I come around I guess- the culprit was a vacuum leak... the booster leaked a bit, which I replaced but the vacuum reservoir had leaks too. Tried the smoke machine to no avail, but the vac gun proved itself and then the water bucket to identify the bubbles- I pulled out the oxyMagneGas & some brazing rods and filled up the leaks then cleaned it and put a coat of Penetrol on the can- maybe I'll order a new can for $40 on ebay if I'm not feeling cheap- but anyway... no more Engine light!!! The best feeling and even better I'm on the road again! I so need this truck right now! Anyway, thanx for the help, I'll continue to watch your vids!

[@curlymyhero]

The viewers diagram of forcing 12v through the pink wire found the problem on the other side through process of elimination. Conversely on the OTHER side of the circuit a corroded 20 amp fuse might have been a problem where the pink wire wasn't seeing a full 12v yet the fuse wouldn't b blown. As a semi-mechanic am I right Matt?

[@SchrodingersBox]

I have never seen a corroded fuse however you would certainly see a voltage drop AFTER the resistance in a circuit for sure.

[@curlymyhero]

thx 4 commenting... quick question-- might one accurately test a bad circuit through a fuse with amps? One problem however would b what the correct setting from a computer, say ECM, might b on say a 10 or 20 amp fuse... Worth it?

[@curlymyhero]

Cuz me--PCM...

[@techsavantlove]

You'll think I'm being a dick, but that's OK. I have to go along with the others, Eddie the Grouch gave the best explanation and definition. Higher resistance = LOWER load. They are pretty much understood to be inverses of each other, and the word Load has a very specific meaning in the worlds of electronics and electrical work._Joe Shearer made the same point equally as well._ We are not trying to be asses here. The word "load" really does have to be used in proper context. _ It implies low resistance, not high resistance, and it implies higher current flow (in relative terms). _With a "low resistance", the current source is will see a relatively "high" load.

[@SchrodingersBox]

+douglas “The flame is dead” lee No I get it. It's explained better in the other parts of the series- remember this is just one part of 4.

[@johnnymalicoat754]

On the last question. Could he possibly blow the fuse in his meter if the ckt draws more than 10 amps seeing the maf is fused at 20 amp?

[@bebeto71-iv4qq]

Hello, Matt. Some 4 pin relays can be installed backward if you are not paying attention. How would connecting them backward affect the PCM? Thank you.

[@SchrodingersBox]

It wouldn’t affect it. You would essentially be installing an open switch instead of a coil. With an open switch the relay would simply never activate.

[@bebeto71-iv4qq]

@@SchrodingersBox I am happy to hear that the PCM wouldn't be affected. Would you mind explaining the open switch instead of a coil part? To my understanding, once current flows to pin 85 and pin 86, the switch will be activated, and if the relay does not have a diode in it that allows current to flow in only one direction, current will flow even if the coil side is backward.

[@SchrodingersBox]

Correct. A coil is not a diode. Current can go either direction through a coil.

[@Agent-nw3it]

This video is not new and my thoughts might have been addressed, but anyway: - Let's say the injector is faulty, but we had luck and it blew the fuse before frying PCM. Assuming that, wouldn't it be the safest to unplug the injector, check its resistance (to make sure it's not internaly shorted) and then continue with tests? Because if we just apply 12V to it, we would fry the PCM, as internally shorted injector presents no load. - On the MAF connector, the viewer assumed the pink wire is power and had an idea of applying 12V directly to it. But if he was wrong, he could have applied 12V directly to the signal wire, and that could be bad? - Also, let's say that the connector has melted inside, cutting the power wire, but shorting power and signal sockets. If we apply 12V to the power socket, we send again that voltage directly to the PCM via signal wire. Not sure how to test this one, how does DVOM work in a resistance/continuity check? Is it a load in the circuit or not? Putting the probability of these scenarios aside, I am happy to be corrected if my logic does not stand.

[@SchrodingersBox]

all sound rational to me.

[@stephenmccann3621]

fantastic

[@SchrodingersBox]

Thank you so much 😀

[@m.b.smoshitoa8325]

HI MART, I LIKE YOUR VIDEOS BECAUSE IN MANY CASES YOU TRY TO USE DVOM WHICH MOST OF US HAVE YOU USE SOMETHING ELSE WHERE IS NECCESSARY. THANKS FOR THAT LET ME ASK THIS. I THINK DVOM ON CONTINUITY HAS VERY LITTLE RESISTANCE. AND I HAVE SEEN YOU ON ANOTHER VIDEO TRYING TO FIND WHICH WIRE WAS NEGATIVE. YOUR DVOM WAS ON CONTINUITY AND THE CAR WAS ON BUT ENGINE OFF. THEN YOU PUT ONE LEAD ON NEGATIVE AND THE OTHER PROBE ON ONE OF THE WIRES ON THE HARNESS. FORTUNATELY IT BEEPED AT FIRST ATTEMPT AND YOU SAID MMMM THIS IS MY -VE. BUT I WISHED TO SEE WHAT WOULD HAVE HAPPENED IF THAT WIRE WAS NOT GROUND BUT FROM PCM. WOULD`NT YOU HAVE FRYIED YOUR PCM? AS I BELIEVE DVOM IS JUST LIKE JUMPER WIRE IF IS ON CONTINUTY I USE TO FEAR TO DO THAT. M.B.S MOSHITOA (SOUTH AFRICA)

[@octavebourgeois5101]

in this video dated 2015 you close with an announcement of doing a video on scan tool operation. Is that video currently on youtube? Thank you,

[@SchrodingersBox]

yes it is on my channel at www.schrodingersboxqm.com

[@xbin87116]

Screw the dvom. Test light FTW!

[@watchrepairing]

Make sure it's a computer safe test light.

[@legallass9905]

Aw, look at my handsome man in the intro!

[@SchrodingersBox]

Thanks Baby! Love You!!

[@m.b.smoshitoa8325]

wonderful video MATT, But i will thank you if one day you may do us video of how things should be. i mean like this o2 s1 should be between o-1 o2 s2 should be approximately 0.5v maf should range between WHAT WHAT TO WHAT WHAT ON NORMAL CAR. ET CETERA. BECAUSE I JUST BOUGHT SCAN TOOL , BUT STRUGGLE TO KNOW WHAT SHOUL BE WHAT IF THINGS ARE RIGHT. BUT AS FOR FUEL TRIMS I EXCEL FROM YOUR BEST VIDEO. HAHAHAHA KEEP IT UP M.B.S MOSHITOA(S AFRICA)

[@SchrodingersBox]

Yes what you are looking for is a list of “normal baseline parameters”. It’s something most people try to find when they first get a scantool. Unfortunately they don’t exist. There are so many varibles- ambient temperature, load, engine temperature, RPM, etc that “normal” is always dynamic. What you do is look for readings inconsistent with conditions AND with other readings. Also failure of a reading to change with conditions is what you look for too. There really is no “fixed baseline”. There are some generalities though. At idle I expect a TPS of under 7% but again - if it’s a drive by wire system and the engine is warming up it should be around 20% or even higher if engine is really cold. A MAF at WOT should read a Lb/min value approximately equal to engine displacement. A rear O2 should not read .5V- it should read .8V at 2200RPM but the most important thing is that it doesn’t duplicate the front O2. But it depends on the catalytic converter temperature.

[@donaldwarren190]

Can the last test inform me of coil pack connection from coil to fuse???

[@websurfer1585]

How about testing with a clamp meter to read amps, with everything still connected, that would surely be a safe way to test wouldn't it?

[@SchrodingersBox]

At the time of this video i didn’t have a clamp. Now I have one and a oscilloscope that’s I use all the time for doing this stuff now.

[@websurfer1585]

@@SchrodingersBox Yeah I'm going to get myself a clamp meter, your videos are great, I'm expanding my knowledge and lot from them, thanks!