How to test for a short to ground (ohmmeter vs test light) 

As a dealer tech with 7 years experience it’s really satisfying watching these videos years later knowing al the answers from experience. This video is a great example of why we learn basic ohms law, watts law and volt drop testing

ScannerDanner is such a great teacher, one of the best

Paul,Im a diesel tech for over 40 years and I want to thank you. I thought I new it all but Im still learning with your videos Awesome class thanks.

This is literally one of the best most useful things I have ever learned about automobiles! Thanks Paul! I owe u!

This video should be required viewing for every high school science teacher & student, electrical-mechanical tech, and ENGINEER out there...!! Many still don't get these concepts, or not well enough to put the knowledge to use in real time (to competently do real troubleshooting / work with-efficiency)... ...Too... Your focus on comparing a circuit with low resistance vs a circuit with high resistance and specifically noting the effect of your body on circuit resistance readings in each of those scenarios makes it super clear and easy to remember... Showing the related math calculations shows a genuine connection between the real world and mathematics & aids learning... ...Also, showing the MANY ways to get measurements and conclusions and next-actions wrong thru improper grounding and hookups and logic is going to save many people time and money and effort (and likely-embarrassment) by avoiding false starts / false conclusions... Thanks for "showing all the work"... Sometimes folks learn best when the instructor follows the side routes that the instructor really didn't want to get into but does anyway (like you just did!)...

So the story is that the car wasnt starting up because the injectors werent getting a signal from the ECM due to the viper alarm stealing some juice supplied by the ICM to the ECM. Thank you for educating future technicians properly and i admire your passion, keep up the good work!

"ScannerDanner." As an "ex" USAF Avionics kind of guy (who, at 79, is trying to learn the concepts of the CAN Buss system) I have to say your class was excellent! I've taught aircraft electronics, and watching and listening to you in class, brought back SO many memories of those days. Asking those "overhead questions" and then having all of those WRONG answers coming back to you, is - disconcerting! :) You begin thinking, "why don't these folks know these answers! We've covered that, in depth, previously." ha, ha.Wanted to specifically comment on your last discussion with the class about the wire with the corrosion, and using your volt meter. As a young technician (a 100 years ago :) I experienced that situation, for real, on an airplane's Rudder Trim position indicating system. I had an 11 Meg Ohm meter with me at the transmitter (a 28V DC system). I disconnected the transmitter's connector and read the power input to ground - was 28V DC. So, I thought, bad xmitter. Installed the new one - did not work. Fussed around for awhile, then an "aircraft electrician" friend of mine came by and asked what the trouble was. Explained it all to him. He reached in his pocket and handed me a 28VDC test light with two leads. Connected it to the connector's power socket and ground socket. It DID NOT light. Friend said, you have a high resistance connection in the wire - probably a corroded terminal (it was) Must tell you, before I did anything else, my friend took a piece of safety wire and stuck it in the 28VDC connector socket and touched the other end to the airframe and asked me to see if the circuit breaker was "popped." It was NOT! Found I had a 20K corroded terminal in the belly of the plane. - that 20K was a BIG resistor. NOW: Moral of the story. The SUM of the voltage drops must equal the applied voltage in a DC circuit. True. With the xmitter in the circuit (ohmic value of around 300 ohms) most all of the circuit voltage was dropped across the corroded terminal - nothing left of the circuit voltage to operate the xmitter. When the Meter was in the circuit, the 11meg of Impedance dropped the majority of the 28Volts - the small remainder now dropped at the 20K resistance. So, it APPEARED that the circuit voltage was fine, but it was NOT. Always carried a test light with me from then on.Had to tell you about this, as this is exactly what you were explaining in your class. Thanks, USAF, MSgt. Ret.

If it wasn’t for this guy he’ such a gift from god I wouldn’t be able to fix the car ❤

MAN SCANNER DANNER YOU ARE BAD A$$!!! I have learned soooo much just watching your videos. I can't go to school at this moment, however these kids have sooooo much of an advantage to learn and do something with their lives, but don't take advantage of the situation... I wish when I was growing up we would of had RU-vid or OTHER RESOURCES to learn.......

Very KNOWLEDGEABLE Thanks 👍 Sir ScannerDanner From Nick Ayivor from London England UK 🇬🇧

Man you make me want to fix cars. I used to be a back yard mechanic know I'm a landscaper. Whell owning my own work trucks there is always issues that I cant afford to pay a dealer. You have taught me so much and want to get back into it.

2.7.17. Paul I can't but wonder how many techs at dealerships would not of been able to bird dog that viper issue! A great case study!.....Those kids in your class really have yet to fully appreciate your teaching style/methods, but when they are out in the real world with real problems, they will come to the realization of what a superb instructor they had! 👍🏽🇺🇸. "Learn it, use it, pass it on"

I have a M.S. in engineering and have also have been a mechanic my whole adult life . Very high quality instructor. Excellent work Thanks

I had a similar case of good spark no injection pulse, I end up being a missing power at the ECM. It has 2 powers directly from battery and 1 from fuse box, fuse was good but female pins had corrosion. That same fuse also powers check engine warning light. Vehicle came from another shop, they putted a new fuel pump, ignition module, hot fuel module, 2 new distributor, ignition coil. Most of my diagnostic skills that I use everyday I learned from Mr. Danner by watching both of his premium and free channels and reading his book. God bless you Mr. Danner and thanks for your magnificent work. (89/Chevy/silv)

How is it that practical, real world people lecture much better than professors who very often 'profess' to know so much. Dan is a very good speaker and lecturer.

Few moths ago I watched this same video I understood little , but now I am washing your Chanel and got your book and is more easy to understand. I’m not native English speaker but you are great teacher and a great person, I wish to leave close to your country to attend to your classes. God bless you Paul.

I wish i had a teacher like you Paul.

Love the case study. This is why load testing a circuit is so important. Always load test circuits. I have seen a few thousands of an inch of corrosion do the same thing.

Awesome video! I’m an electrician and this method of process of elimination is used everyday. You hit the nail on the head with this video!

Nice class Paul. If they listen to you and watch your case studies they will learn a lot!

Great lecture! It must be hard to keep on subject sometimes with the questions and all, but you pulled it out as always. Thank you for your patience!

I'll be watching this same video over & over again until it sinks in. Thank you for posting it.

Enjoyed the video Paul as always!

Great video as always Paul! Dude, seriously I can’t thank you enough for all the stuff I’ve learned watching your videos. I don’t know why I wasn’t subbed before, but I am now. Keep it up bro

outstanding tuition !!

Great case study. The ohms law math for parallel resistors is 1/ref= 1/# + 1/#. So, the reference resistance would be 1/12 + 1/400,000. Then, the reference resistance is 1/0.0833= 12.048 ohms. You’re an excellent instructor.

Don't sweat the formulas, learned magnetism and electronics in college physics and could not remember that formula either. It was great to see the practical application in automotive troubleshooting. I have always been frustrated with my inability to apply the college education to this. This video was very helpful, heck it was really good. Thanks.

I wish i had the chance to learn in your school, iv had to teach myself along the years as i follow and you ask your students i normally have the right answer, without any formal training. By Gods Grace. I still am learning as i go along in the field and add more understanding and depth as i learn from your videos. Thank you for your time and effort you put in sharing your knowledge. God bless.

Wonderful and smart, That is Knowledge with teaching skills. Great job

Scannerdanner you are incredibly. I'm one of your new student; God bless you 🙏

Aww man im excited!!! Just found out about your online course and ill definitely be starting next month! I've been working on vehicles for sometime now even went to my local ComColl but didn't finish due to a back injury. Im going back but ima learn so much from this course in the meantime! I really enjoy all the RU-vid vids keep up the excellent work!!! Looking forward to classes and future content 🤘👍

fantastic , just brilliant stuff , always said if you have a great teacher that can put it to basics so that everyone can understand , real champion this guy.

GREAT AND EDUCATIONAL VIDEO. 5 ***** DEFFINITELLY. CLEAR AND CONCISE AS DICTIONARY! GREAT JOB AS INSTRUCTOR ALSO.

Superb Paul,you really are gifted at teaching 👍🏻

Excellent lecture Paul. My note books are getting full!

Paul when i listen to you it hurts my brain you are God of diagnostic.

Wow. This lecture saved me $3100 in repairs quoted by the dealer to fix why I had no spark and no injector pulse. You are my hero. Here I am 2 weeks without my car to make it to work taking Uber to and from work but this gave me the knowledge and information to diagnose and troubleshoot things myself. You take donations? You deserve it my friend!

.some time i watch your videos .you're awesome good explanation thanks

I am watching from Turkey ...thanks for useful knowledges

Excellent lecture thank you so much.

What an excellent case study! When you told the story of missing the high resistance short to ground and replacing the ICM, I thought, I would definitely have made the same mistake. The only thing better than making a mistake yourself to trigger hard memory is watching somebody else demonstrate the same mistake. There had to be internal inline resistors on both the ICM side and the ECM side. Extra resistance inside the ECM allowed the natural signal to bypass the ECM on its way to ground, and extra resistance inside the ICM dropped the square wave signal to an undetectable level when you looked for the signal initially. It had to be a 'Goldilocks' resistance at the short -- too low and the scratch test would not have triggered fuel injectors, too high and you would have detected a signal when testing the wire initially.

Directed (Viper) wire color violet/white is tach input on their remote start systems. Has no alarm function. They only cut the crank wire.Probably was a combo alarm remote start. If the wire got chafed to ground or something went bad in main module of the r/s it would cause this.I diagnosed a car (camaro) long ago where this happened. Installer did not grommet the purple/white through the firewall. Just drilled a hole and called it good. Wire started to wear through and the car would barely run. Love the Vids! Thanks

You were on the right track, it is product over sum , a 3ohm and a 2ohm in parallel = 3x2 = 6ohms , 3+2 = 5ohms, 6 ohms ÷ 5ohms = 1.1ohms .

I had a similar case that kicked my ass a few year back. In my case it was a remote starter that had failed. This module was deep inside the dash behind the climate controls and the antenna was hidden cleanly between the roof line and windshield. Customer had no clue and no remotes (used car also). Found a resistance to ground of about 2k. Followed the wire and found the splice. Took me a little longer than Paul to find it... ok ok a lot longer... but I found it. Never have I seen a remote so well installed. I doubt I'll ever see that again, but I have learned from it and this video brings so much clarity to the hole thing. I finally fully understand what was going on. Thank you

Amazing i missed this video. I had paised with the class as Paul had asked what is wrong with just connecting the meter leads to the end of the wire. Its not a short to ground test. Makes sense. First you set highest rating on ohm setting and then with neg touching body of car, touch other leed to another part of the car to test neg connection good. Then pos touch leed to test for shortto ground. Awesome I never knew this. Now I do.

Your students, with their line of questioning seemed to sidetrack you for a time, but I'd like to bring you back to this important question at the point of sidetrack: You mentioned that if the circuit DID NOT have a short to ground that the meter would max out and read ohm with an ohm sign ... so now the question... What would the meter read if there was a short to ground when testing on the wire/circuit in question between the ICM and ECM? .. thanks for a great tutorial.... I knew you were a great mechanic but seeing you teach this class, I was amazed at you abilities to get things across.. many thanks SD

Hey Paul as part of an electrical class extra credit project I showed how the parallel circuit fraction equation is derived from simply using kirchoffs law and ohms law. I'll post it on the forum it's not as mysterious as people might think and involves simple algebra

Nice one.. series and parallel circuit... Good Job.

I thought, "I have to wade through 40 minutes on my phone to find the test method!?" 10 minutes in and I'm wondering if I should tell Toyota I want to transfer from my corp seat to service garage. Brilliant, sir!

You are a Great Teacher..

Good job sir. I liked your lecture, very informative. Keep up the good work.

This video is totally and utterly fascinating and educational you know Paul I have been fixing computers for 15 years and I thought I knew a bit of stuff about resistance voltage etc but I have learnt more from you in the last month then I have in all that time thank you

Great stuff as always danner thanks so much

Very intriguing and superb video.

great video paul, as always cheers from ontario can

Very knowledgeable guy great channel 😊

Excellent lesson.

Sir your 💯 % right on last meter voltage drops that point ,👍

Excellent explanation. TQVM

I know I've seen one of your training videos where you explain how an open circuit with super high resistance reads less that source voltage due to voltmeter impedance. Just can't remember which one. Thanks for the vid.

This is what I love 👏👏👏 This is what I've been looking for

Good teacher good knowledge pls help me out how does spark plugs work thanks

I am so glad I found this video, this helped me alot thanks Any advice on what kind of a icm to use in the gm’s as a replacement ?

Great video thank you from Egypt

Scannerdanner you are incredibly. I'm of your new student

Amazing video Paul

at 36:35 mint ,the only way to prove your point that open circuit voltage is equal to voltage source no matter what resistance value you have ,is to use labscop,As you said multimeter internal resistance will create current path which will create voltage drop less than Voltage source .bottom line a wire without a load (no current flow) voltage reading should equal source voltage..Good video ..no body should argue with you ...you are a great teacher .

Incredible class, thank you so much. Very didactic

Thanks from Lithuania

wow this is going in my favorite, favorite, favorite videos 👍😜

Nice video, from Peru

I am vary impressed with the way you teach my greetings Hussein from Iraq

you are a good teacher in the world danner

I REALLY wished I would have had someone that ACTUALLY TAUGHT class when I was in tech school. My instructor ONLY lectured class on electrical. We were left with our text books for the rest.

Thanks SD.

Great lecture

Yes I'm qualified. I attended RU-vid uni. I have a combined experience of 100 years from watching people try things.

aww thank God. i miss ur in class lectures. back to ur old days, lol

Great video , man! One time ABS-module had green stuff from connector to in te module it self.... wire connector was allso melted a little. So before fixed ABS module was Installed, i check ABS-wires (dos it just need new connector or little more), why that connector melted. in firsth place? Car battery was out and my multymeter showd that my main power wire had a conection to the car body even without the fuse in place. ...The melted plastic connector made the connection betwean main earth and postive wire, without metals tushing.... After that learn curve, i allways test connector houseing to the wires before i take down the car to find nothing is outofplace. as plastic(specialy melted one) can make your ohm meter go wild too :D

This is some great stuff :D

As an electrician before we perform an ohm test we do a lead test by obviously touching the leads together and seeing that 0 ohm reading .

If the square wave is 5 volts and the test voltage is 12v, does the 12v not harm the ECM? Excellent teacher.

Just like SD said, regardless of the resistance in line, the voltage makes it through. But once you connect the non-infinite internal resistance of the voltmeter to it, the voltage will drop according to Ohms law, because current is flowing, posdibly really tiny current, but still there, leading to voltage drop. The plastic on the outside of a positive battery cable is at 12V, but the resistance of the plastic is incredibly high, so very tiny current will ever flow through it. There are no perfect conductors (at least not at room temperature), and there are no perfect insulators, just very good ones in each category. All conductors are insulators to some point, and all insulators are conductors, it's all a matter of perspective. If your only going to learn one way to calculate parallel resistance, learn the inverse rule. It works for two or two thousand parallel resistances. Never forget that the total resistance will always be less than the smallest individual resistance with parallel resistances.

where was this guy when my stupid truck started acting possessed? Great video man

NO STALL PAUL LOL ,BRING YOUR CAR TO SCANNERDANNER AND NO LONGER WILL IT STALL !!! LOL , i enjoy this video very much brother ,these classroom videos are off the chain !!!! enjoyed the ohms law lesson too ,its been decades i really thought about them ,this is where everything started !

bad ass info appreciate it

you are the best

I know what you mean keep u the good work,

EXCELLENT

Good class

Good knowledge thanks sir in Peugeot diagram we have two or three ware which one can put the test light on thanks sir please feed me back

You guys need an Ugly’s book ! It’s an electrical reference book we use in the electrical trade, it would be super helpful to you guys ! Get it at the home depot for 20 bucks. It has all the basic formulas and calcs explained.

Paul did you have a video on that van with the viper alarm system? I swear I saw it before. If so can you provide the link?

I like this guy))

This is amazing

Great!

I'm always super leary of manually sending signals to the ecm bcos I'm scared it'll fry it? How did you conclude that the 12v from the test light was safe to use on the ICM bypass?

good video, but a better tool for checking for a short to ground would be an insulation tester. Disconnect both ends of the wire and check between the wire and ground using 250V or more.

I met the same situation with meter impedance when measured voltage on low current circuit. I had wrong measuring due to low impedance my meter. It must be 10 Mohms or more.

o2 sensor signal wire bias voltage testing...viewed it at lunch time :)