MUST WATCH - Can a Test Light Damage Your Cars PCM ?

[@myRatchets]

Hey Do it yourselfers, sorry for not uploading videos for a while, I've been super busy doing projects around the house and with my election campaign. Will be uploading soon and updating you all. cheers

[@myRatchets]

There's a good chance both my opponents might not make it to the election so not giving up.

[@kdash3215]

Great to hear! We had the search brigade on standby the whole time. Best of luck!

[@Dfygy]

What election?

[@fastrice3461]

Thanks for the update. Hope to see you soon!

[@kamutiub]

What?what are you running for?any links for us fan to follow the campaign?

[@x-man5056]

The gynecologist joke was gold. LMAO I'm stealing that one. Bless you for trying to squeeze a 40 hour basic electricity class into a 12 minute video. Important thing to remember is that Volts are pushed, Amps are drawn. Example: a 12 volt battery in a 6 volt system will fry anything that gets turned on regardless of amps drawn but you can run a small 12V test light with power from a 12V, 800 CCA (Cold Cranking Amps) battery without worry. AND, electricity, regardless of voltage, amperage, or if AC or DC always follows the least resistive, path to ground. BUT, the higher the Voltage (not amperage), the more resistance it can overcome. It's high voltage (like spark plug wires) that will let you know you really screwed up, quickly. Happy New Year!

[@WestCoastUSA546]

It was gold only for mysoginists like you and those who make references to women in a way that isn't warranted, like this insecure prostate examiner who made this video

[@x-man5056]

@@WestCoastUSA546 BWAHAHAHAHA. I don't remember the joke but if I said it was funny then indeed it was. Who appointed you the decider of whats "warranted"? Laughter is always warranted. On behalf of myself and the prostate examiner, ...F.O.

[@bikingfencer]

@@WestCoastUSA546 so you make a joke about prostate examiners

[@spelunkerd]

Well stated! I'm willing to bet that the vast majority of misadventures happened because of more glaring ignorance, such as accidentally jumping the high amp side of a removed relay into the computer ground relay pin for the control wire. In fact I think I remember ScannerDanner telling a story where he did just that, killing the PCM. I've seen guys apply 12 V with a power probe straight into a communication circuit, relying on the internal resistance inside the PCM to come through. Not wise, even if they do get away with it. Yup, test lights are incredibly good at limiting current, and you get a bonus light to tell when significant current is flowing. Also your remarks about current are spot on, power is what fries connections, and power is the product of resistance and the _square_ of current (voltage drops out of that equation). The test light is critical insurance, especially if you use a low amp light. Many guys use an LED test light when testing computer circuits, or even, as you say, the human body. All that said, I don't know how the op amp devices inside the PCM are designed to react to voltage the circuit is not designed for. There's something very appealing about not sending anything to the PCM that it doesn't see every day.

[@wynnhorton1208]

I am trying to diagnose a power window problem, so am considering buying a test light, voltmeter, or multimeter. I play around with computers a bit, too. Can I just buy one device for PCs, cars, and other home stuff?

[@spelunkerd]

@@wynnhorton1208 Learning practical circuit diagnostics is a process, and in the DIY world the progression can take decades. I would start with an inexpensive multimeter, and an incandescent (not LED) test light. A good place to start is automotive diagnostics.

[@wynnhorton1208]

@@spelunkerd thanks. I am researching multimeters right now and leaning towards the AstroAI 6000 or maybe the cheaper AstroAI 4000. I've decided to skip the test light altogether. I'm looking forward to learning, because mechanics aren't cheap and neither are parts.

[@spelunkerd]

@@wynnhorton1208 Your first multimeter won't likely last very long so don't spend too much time researching the topic. One of the most important lessons is not to measure inline current without enough resistance in the circuit you're testing. Use ohms law to calculate how much current you'll see, and make sure it is under the limit of your meter. If you put both leads across a battery, hook up to measure current, you'll watch the smoke escape from your precious meter, ha ha. Ask me how I know, it is a humbling right of passage. Quality meters have a fuse you can replace, cheap ones are destroyed if you do that once. By far the most critical lesson you need to learn is how line voltage dips down when you get electrons flowing, so called voltage drop testing. The easy way to do that is with a test light, but you can do it with other sources of current draw and a multimeter. Once you learn drop testing fundamentals, you'll reach a whole new plateau of understanding. Happy sailing!

[@wynnhorton1208]

@@spelunkerd dang, I almost bought the one with the fuse and did realize the importance of it, but the other took batteries that could be recharged and I liked that. Thanks for your advice

[@rnieves22784]

Is everything ok? Haven't seen any new videos from you in a while I hope everything is ok. Your videos are great hope to see one soon.

[@nicholaswarner1143]

Wondering the same thing 😳

[@JonDahl]

I came here to ask the same thing. Five months is a long time!

[@gmax341]

Same. Honestly forgot about this cool dude until one of his videos popped up in my feed. Now I'm curious too.

[@YZFR1is]

Glad many people are noticing~ Hope everything is ok, really

[@JonDahl]

He’s updated us letting us know he’s been busy with an election campaign! He’s okay! 👍

[@joshuapruden6497]

"These electrical engineers that design this stuff"... Jerkoff hand motion.... Priceless!

[@Ry77x]

Hey man, great videos. I’m a new subscriber and inexperienced on working on cars. Besides a Haynes catalog, old guys at work, and a few other KZbin car guys, you have been a big help with your knowledge and videos. Simple, clear, and informative. Top 4 KZbin car mechanics that I follow. Excited to see what you put out next. Keep up the good work brotha. 🤘🏽

[@Miketz]

A couple of observations: 1. "It's the current that does the damage, not the voltage". While mostly true, in practice it is the voltage that causes the current in the first place. (and it is voltage that kills electronics ) 2. Electron flow (from - to +) while technically correct, it should be ignored as it just causes confusion. Convential Current (from + to -) is what everybody else uses. 3. I am an electrical engineer, and I am confused after watching this video. You should have just lead with "Yes, a test light could (in theory) damage a PCM, the engineers have built lots of protection circuitry around the inputs to prevent this happening".

[@rpsmith]

"2. Electron flow (from - to +) while technically correct, it should be ignored as it just causes confusion. Convential Current (from + to -) is what everybody else uses." No! Just Electrical Engineers are science deniers that pretend electrons flow from positive to negative! The rest of us have been properly trained. Aren't colleges great? They turn out socialist by the millions and Engineers that think backwards!

[@VashthStampeede]

Point number 2 is for people who don't understand that hooking the negative terminal to chasis ground makes the whole vehicle a source for electrons. With this abundance of electrons, it's easier to tap into them when there's something that needs to use them. The positive just provides the path back to the battery.

[@mukwati]

point 1: When dealing with auto electrics, mostly they only need to know if there is a potential energy for a a specif point on any circuit and most of them are open or tested before a connection of interest, this is why he says "tapping-in" at those points isn't affecting anything, especially if the circuit is open (manually/electronically by a board) thereafter.

[@pigeonsil240sx]

what if i hooked test light to a 5v source to test 5v ref and computer parts that take 5v by getting a 12v to 5v usb cigareete plug adapter,then cut a usb cord and plug this into the 12v to 5v adapter and find which wire is the power/ground and use this to hook test light when probing these 5v computer circuits? this would also drop some of the amperage draw from test light correct? would this be the way to go?

[@joeynobody1138]

Remember folks he is NOT an Electrical Gynecological Engineer, but he does play one on KZbin.😉 Great video.

[@Cali_moonshine909]

I used a power probe and injected 12 v on a 5v ECT sponsor connector like a dummy and had to get a new module… well a used one actually and had it cloned with the old one .. 🤦🏻‍♂️ lesson learned lol never inject voltage into just any wire especially if you don’t know what your doing..

[@tommysmith3145]

I learn alot from ur video's. Could not stop laughing though, when u said " oh my god, im dead".

[@wheeldealstt5445]

Who needs college when there's guys like this on KZbin 😂😂😂

[@pesapesic4788]

10:43 hand move, lol

[@SirBisgaard]

Natural instinct.

[@ynsmsd8789]

A body language used by techs in specific circumstances. Other way it means ( fixing B.S issues)

[@jarnorajahalme28]

“...supposed to spend a lot of time...”

[@andrewthompsonuk1]

It does depend on how big your test light is. Go for one with a small bulb. All the pcm drivers that could be damaged will require more than about 500 mili amps before they may fail so a 200 milli amp test light is is fine.

[@overload3996]

No, set scope trigger to capture, Place your current clamp over the POS on your battery. Drop your 200 mA test lite to pos and catch the current.

[@mikepettengill2706]

The big danger with a test light like that is that you can provide voltage to a coil somewhere on a solenoid and "jump start" your engine or some other system that you have your arm sticking into or are laying under. Be cautious what you test with the lights, it is really just a wire and you are basically connecting things to the battery to see if the other side of the device goes to ground or power. Better to use a meter with one of the additional probes that will show you what is going on if you know what you are seeing on the meter. Also, never push the pointy end through the insulation. You will wish you didn't in a few months when that wire starts to corrode and the resistance goes up and you keep changing "bad" sensors or whatever and it just never acts right again.

[@frankd.brennan6520]

I've heard that static electricity can blow your ecm. It was always good practice to disconnect the negative. I know that systems have gotten more sophisticated, but which one's and when. I think it's better not to take the chance. Just like giving someone a jump. There's a lot of controversy about the weakening of your electronics that can show up months later. Just my 2 cents

[@freedom1niner575]

Never stop pretending

[@tonijohnson09]

I love this guy 🤣🤣🤣🤣 Very good video, bro. Can't leave that out.

[@kevinjohnson9736]

What has happened to the channel? Is he still making videos?

[@MucaroBoricua]

I'm an electrical engineer and you are on target.

[@Mike-gr2ok]

@Sam S nice one Sam 👍

[@MucaroBoricua]

Sam S, @2:31 he clearly says that Ohm’s law is correct all the time. Too much ear wax can distort sounds... just saying. I should’ve stated that I was reacting exclusively to the discussion about how the multimeter works. Ohm’s law works all the time, but only in purely resistive circuits. An incandescent light bulb can be modeled as a variable resistor that depends on the filament temperature. If you had the resistance curves of a given filament, you could verify that even then Ohm's law applies. Stop misinforming people.

[@MucaroBoricua]

Sam S, your knowledge and attitude are so wrong that they don’t deserve further discussion. You just hate engineers because we make many times what you make. I’ve seen many of you and your pseudo science. Take a basic electrical course and you might be straighten up.

[@scattkiwiman]

but maybe need be careful though. Suppose you branch the test light to the 5V output that goes to eg. map-sensor (other branch of the test lead to ground) . You will draw 250mA extra to that output. Maybe too high for that particular output (cannot be sure unless you have the specs of that ecu, in most cases you don't have it). When you connect a V-meter to that 5V output it will do no harm because the V-meter has a high resistance input and will not draw any extra current. So I would never connect a test light to a voltage output from a ecu.

[@averyalexander2303]

I know that a lot of PCMs have overload protection on the 5 volt reference circuit and won't be damaged even if it is shorted to ground, but I agree. ScannerDanner actually has a couple videos showing this

[@scattkiwiman]

@@averyalexander2303 yes sounds logic there would be a protection built in. Thanks for that channel looks interesting !

[@Xibyth]

Considering you can get a multimeter for about 10 bucks, it is a far more powerful troubleshooting tool than a test light and is totally worth it to both own and learn to use.

[@Xibyth]

IAMNOSLEEP A test light only confirms there is current running through the system, the battery provides the load. To test continuity (integrity of a circuit) you test the impedance to see if it is open or closed, which can be done with a multimeter.

[@Xibyth]

IAMNOSLEEP will do.

[@Discretesignals]

@@IAMNOSLEEP that why if you using a meter, you measure the voltage drop of the circuit while it's active. Don't rely on a 250ma test light to load a high amp circuit down.

[@maxagent86]

Excellent video, but I’ve always understood that the convention of current flow in a car as going from the positive to the negative side of the battery, not the opposite as you stated at the beginning. That is why we should always disconnect the negative side of the battery first, so as to eliminate ground to all circuits. Please correct me if I am mistaken. TIA and, again, great video (long time subscriber here).

[@maxagent86]

Johnny Blue - this is precisely what I‘ve always understood to be the case. Yet, this also means that the negative side of the battery is where ground is. And ground is where the electrons go (even though the symbol is negative), no?

[@maxagent86]

Johnny Blue, thank you again. That helpful link you listed states that, in a DC circuit, because of (confusing) convention, current flows in a direction opposite to the flow of electrons. Is that why, in a car, the positive side is called “power” (even though that is not where the electrons are coming from)? I’ve always thought the term “power” referred to where the electrons are flowing from. Messy...

[@imtruth69]

I have been an electrician for over 40 years and I am telling you that some of your info is spot on but on some other stuff you could be steering folks wrong on some of the stuff that you are saying. For one thing when using your test light in series with your DMM you say there is no current flowing. WRONG. Just because the light does not light up does NOT mean there is no current flowing. True that the light bulb will limit the current but there is enough current flowing and voltage to damage some electronic components.Just saying, buyer beware.

[@pashko90]

For a lot of circuits can be burned with 300ma current drow. I did fix few of them. Specially for camshaft/crankshaft circuits. Try to burn a Led with 300ma 12v, you will probably burn it.

[@CameronDC-Grimes]

The 200-270mA is the constant flow of current not the initial touch that jolts it to 1-1.4Amps then quickly goes down to 120-300mA depending on your bulb and coil test light brand. I was watching ScannerDanners channel and he said he's never had any issue with test lights and computers using his OCT incandescent test lights. I believe he said he never uses incandescent bulb testers on injector drivers because 200ma to 1A is way too high so he actually uses a LED test light instead of incandescent bulb testers which is his preferred method.

[@pmgear]

@10:43 subtle but elegant right hand movement😉

[@td2055]

HEY... What's up? I am missing your vids. I enjoy your vids - viewing from Trinidad and Tobago

[@mayk3lll]

I changed my test light globe from incandescent to led to limit the current flow even more. Incandescent globes draw more current than led is my understanding

[@greggc8088]

A test light can surely overload a low power circuit but I would much rather see a tech with one on those in his hand that a dang power probe. All those should be thrown in the garbage. I work a techline and you wouldn't believe how many modules I hear (actual beeping) get fried by 12V being pushed in a signal or control circuit by a trigger happy tech with a power probe.

[@jcmobilediagnostics8611]

Greg M power probe is an awesome tool but you have to understand circuit design. I typically use test lights but in some cases power probe saves time. You have to know which tool to reach for given the situation.

[@Dtapia63]

Why blame the tool? the tool has its purpose and if you use it wrong you pay the price......

[@aaronmcdonald4944]

i love the sense of humor in all your videos

[@redlywaxer]

I'm still not taking chances on expensive electronics in cars. I can do everything needed with an inexpensive high impedence VOM and do it better. I save the test lights for house wiring and the pre-electronic classic and non-electronic vehicles. I have not used my 12V test light since the last time i checked static timimg on a car with points ignition. When the points open and break contact, the test light comes on, showing you the position on your crankshaft where #1 cyl spark is set to fire.

[@bwest-yq3uc]

Enjoyed you video...while we had them. Wish you well. Hope to see you farther down the line.

[@yllibtaog]

Spoiler alert, YES, you can instantly fry your pcm with a test light. Always use a DIGITAL volt meter. An analog meter can fry a pcm the same as a test light.

[@overload3996]

Now put out a video with a scope current clamp around the .200 Amp test lite, and watch it current rush 2.0 + amps, which burns out the .200- .400-.500 mA drivers. So yes a test lite can easily fry a PCM driver!!!!!!!!!!! ( relay, etc )

[@overload3996]

@@charlesgould8436 OTC has a PCM safe tester I use. I just showed my son other day the damage to transistor on a curve tracer with us using a .200 mA test lite.

[@MindsDozer]

@@overload3996 what do you guys think of the Lisle computer safe test light?

[@overload3996]

@@MindsDozer I use the OTC computer safe test lite. Not sure of the Lisle, I could look it up. Price wise maybe better then OTC ??

[@overload3996]

LIS34550 is safe, same operation as the OTC. But remember the neg to pos LEDs is at what voltage to current Red or Green. My OTC was green up to about 50 mV, so voltage and current play a margin with these lites.

[@pamelavance648]

​@MindsDozer what was the answer or results

[@ShaunHensley]

Voltage is pressure, current is flowrate

[@markdixon392]

That analogy is often used to describe elementary DC systems, but it is much more difficult to translate to mechanical systems. One more appropriate analogy is voltage to force and current to velocity (where resistance is friction or damper, inductor is mass, and capacitor is spring). The pressure analogy is much more difficult to understand when considering sinusoidal analysis since you have to bring in calculus and transforms. I understand the desire to use the touchy feely mechanical connection in the beginning, but electrical is mostly conceptual (described by math). If you want to bring in an analogy, the math has to work both ways.

[@ShaunHensley]

Mark Dixon force is pressure and flowrate is velocity. Those words are synonymous

[@markdixon392]

They aren't really synonymous, and hence the complication I mentioned... pressure is force per area, and flow rate is volume per time. The math is simpler when force and velocity are used. The voltage across an inductor is L*(dI/dt). Current through a capacitor is C*(dV/dt) where V is voltage. In the mechanical system (not water through a pipe, but mass/spring/damper like a car suspension), Force on a mass is m*(dv/dt) where the v is velocity. Note that dv/dt is acceleration (the derivative) ... you know the simpler form as F=ma. If you add area and volume, managing the units is hard. Try it... what is the math model of the pressure of water going through a pipe in your analogy? The description above may not make sense without an understanding of calculus.

[@AstroTomK]

@@ShaunHensley In non science terms if it works for you. Voltage is potential difference 'like' a water dam levy, current is 'like' the flowrate of water. note velocity of electron is constant doesn't change, the quantity or density of electron flow is current. Force is mass x acceleration measured in Newtons, (acceleration is change in velocity) Pressure is N/m^2 _edit: momentum is mass x velocity_ _my description is simplified, as electrons can have different energy states, so the electron flow above is meant to convey the energy transfer by elections_

[@kiyoponnn]

@@ShaunHensley 🤣🤣🤣Found the noob

[@antoniospence1710]

I damaged a honda civic pcm once with a test light in fact its the type of bulb in the test light that makes the difference

[@amir3992]

My lancer's pcm, all the speed sensors, Map sensor, 2 more sensors in the tranny and TPS were all destroyed by testlight haha

[@kdash3215]

Hey brother, fellow wrencher here. Hope you're doing alright and come back soon. Checked your socials but they're quiet

[@sanjay4real]

I agree...he is one my favourite youtubers...have learned so so much from him....hope all is good in his world!

[@kdash3215]

@@sanjay4real Check the newest comment. He just informed us about working on his election campaign.

[@sanjay4real]

@@kdash3215 wow that's great... so glad he is okay! thanks @Alucard for the note to check latest comments!

[@kikcodog]

Think of voltage as being a mountain with a pool of water at the top. The higher the mountain, the higher the voltage (potential). Think of the current as the river that would flow if you give it a path from the top of the mountain to the ground. The resistance is how wide, deep, steep, rocky, etc you make that river between the top of the mountain and the ground. Voltage = Current X Resistance often written as V=I*R. Changing any variable (V, I, R) effects the others. In general, we can change V and R and I (current) is just what results since, in general, it is very hard to make a constant current source. Now, as for this video, people are probably talking about the active probes that allow you to apply power with the probe, not a simple test light or DVM. These active probes are more akin to a jumper wire from the battery. Incorrect use can send power through an output (designed to apply power, not receive it), etc, overpower an unprotected input, etc. Friends who are fleet mechanics tell me these probes have been banned in certain shops because they were blowing out PCMs and transducers through improper use.

[@pashko90]

@@IAMNOSLEEPol, try it on your own car. I did fix few computers after a test probe "diagnostic".

[@pashko90]

@@IAMNOSLEEP so, still during 40 years you didn't learn how to use multimeter? LOL.

[@kikcodog]

​@@IAMNOSLEEP Engineers design for the expected failure modes but at no time during the design process did an EE say. "Gee maybe we should account for someone putting a 12V, non-current limited signal on this input or output" which is what these active probes are - a jumper wire .The protection used depends on how the ECM or other circuits were designed and what components were used. What's driving (energizing) the outputs and what's protecting the inputs? Sometimes inputs are protected with a combination of diodes, Zener diodes and RC circuits. Sometimes not. IC inputs usually have built in diodes to protect against high voltage spikes and even they'll blow if the voltage last more than a few milliseconds. An input expecting a maximum of 5V many not survive a 12V, non-current limited probe suddenly energizing it. Sometimes putting 12V on a 5V output will damage the semiconductor driving the output. Using active probes (i.e., probes capable of apply a voltage and current) to drive inputs and outputs is risky without knowing exactly what you're dealing with. Most EEs wouldn't do it without a complete detailed schematic. You can be off 1 pin and cause havoc. Usually transducers are designed to fail as an open and not a short. If there is a potential for shorting fuses are used. Can an IC drive a short? Sure, you can current limit the output but, that's not the same thing as energiving that same pin with an active probe at 2 or 3X the output voltage without any current limiting. It's not quite as simple as your explanation. The other thing to understand with ICs is they don't always fail completely like a fuse. Sometimes they just get damaged and begin to operate unpredictably and fail intermittently. That is why ESD is such a big issue and millions spent each year to mitigate it. Simply handling a PCB or IC without ESD protection can cause damage that doesn't show up right away, or worse, comes and goes. There's a reason big shops have banned active robes and it's not theoretical. It's based on having to buy expensive ECMs techs have accidentally damaged during troubleshooting.

[@kikcodog]

@@IAMNOSLEEP The topic is the use of active probes. SInce I was the original commenter, I understand the topic very clearly. Reminds me of one of my favorite quotes, "You can't teach a man what he thinks he already knows." And yes, I understand I am wasting my time as far as your concerned, I rook the time to help others who may be trying to understand the issue(s). Happy New Year!

[@kikcodog]

@falchulk That's another good analogy. Voltage is the water pressure at your faucet. The Resistance is the diameter of your hose and current it the rate of water flow. Actually that is one ppl can probably relate to even better.

[@averyalexander2303]

Nice video! One way I suppose you might damage a PCM with a test light is if you overload something with it. For example, if you connect the test light to the control side of a fuel injector while the engine is running, you will be drawing more power through the PCM than it was designed to provide since you will be lighting the test light as well as firing the fuel injector when the PCM was only designed to safely provide enough current to fire the injector. I don't know that this actually could cause damage since the PCM might have some sort of overload protection. But I know that a lot of PCMs have good enough overload protection on the 5 volt reference circuit that it can be shorted to ground and not do any damage. If anyone knows if this could actually cause damage please let me know, I'm curious.

[@SinGz86]

It can ... I was testing my car with a power probe on my AC sensor with the engine "on" to the ecm ... The the two combine currents (running engine + power probe 12v) fried my ECU. Moral of the story...even if u don't f**Ked up, u can get a new cheapy ECU from salvage $77 and bring it to dealership to reprogram it for $100.

[@averyalexander2303]

@@SinGz86 A Power Probe is not a test light, it is very different since it provides no resistance and can send 12V directly to a circuit or ground it out without the resistance of the light bulb. So effectively a Power Probe is no different than a jumper wire

[@SinGz86]

@@averyalexander2303Essentially, a power probe is and can be used as a test light. It can be very useful as it can test ground and circuit connections with an added twist of sending 12v. Currently, I use a test light most of the time and made sure that I pulled my negative terminal out from the battery to break the circuit from the lesson I have learned.

[@averyalexander2303]

@@SinGz86 Oh okay I never used one. How much current will it pass in test light mode?

[@SinGz86]

@@averyalexander2303 I'm not sure, but it hooks up to the battery 12v and whatever amperage the battery has. It's an effective tool but the users like myself must respect the tool and really understand which wire is the ground, ref circuit, and circuit to the component like the ac pump. Laziness and neglect is the moral of my story of lesson learned.

[@bwest-yq3uc]

Sill doing videos??? have not seen any lately. All Your subscribers are hoping that you are ok and the covid19 has not slowed you down. Good Luck and hang in there.

[@1.9tdilove71]

Gynaecologist😀😀

[@mradrianzavala]

Can you please do a top 5 Most Reliable Vans for big families.?

[@Assertiveman]

Before using you want to make sure your main ground to battery and chassis grounds to chassis are good if you had a even a slightly loose battery terminal, it won't displace current right

[@arvindsingh-qp7rg]

Hey man where did you go ! I really miss your videos .I hope you and your family are safe and well . Please make a video soon , Thanks

[@ghost37666]

8:18 "Oh my god I'm dead" Now I am dead from laughing 😂

[@williamwhite9767]

I understood what voltage and amps were when I equated them to pressure and flow in a water pipe.

[@daveallen4194]

Hanging on to the ohm meter wires as you did, shows high human body resistance to current flow when you skin is dry. However, you missed a great teaching opportunity by neglecting to lick your fingers, and then grabbing the wires a 2nd time, which would have shown much less resistance (ohms) and therefore a much higher current flow with the same voltage. This lesson would show very well why you don't stand in water (bath tub, wet basement floor, etc) when working with 110 vols, or 220 volts, etc. A wet body in those conditions can get you killed very quickly, because it conducts current much better.

[@patagualianmostly7437]

Dave....Well, to be fair he did mention the old 9v battery on the tongue...you certainly feel that because of the damp/wet tongue.

[@fastrice3461]

Ohhh so is that what electrical engineers spend their time doing? Another great video, thanks!

[@WorthlessWhips]

I thought I had damaged the PCM, but it turned out that I had forgotten to plug the idle air control valve back in on my 305 Tbi! Thanks!

[@MucaroBoricua]

LOL Most of us are practical gynacologists and boobologists.

[@LeverPhile]

1:52 ... amateur yet very proficient motorboater!!

[@ghassanalfarra8935]

Some are even proctologists .. 😁

[@augustaking8]

With the older meters we worried most about pegging the needle and wrecking the meter movement.

[@squirrelkilla7371]

7:52 This is going to make an episode of Ridiculousness

[@jdrs4214]

If you have a decent, cheaply made Chinese multimeter..... like the one this gentleman features in this video..... Please don’t leave it in direct summer sunlight (especially at 108•F day), much less in a hot car. I left mine (which was just like this one here) out in the sunlight once, after having gone to lunch. I found it warped, and the display was horizontally half lit. You’ve been warned!!!!

[@clifbrewster8822]

I'm new at this kind of mechanics I've alway just been a parts changer so thanks for the info and dammit wish I had your hair on top of my damn near bald head !! Those were the days ...

[@lewisbeshers1946]

Bill Nye The Car Guy? Very informative vid. See you next year!

[@hanielbomb]

Dude where are you man?

[@kwaichangcaine8234]

Thanks I enjoyed . You have me wondering now if age can be measured in ohms

[@shawn396hoss]

When you grab the test leads you should have... Oh my God I'm dead! XD lolol naww I'm dead

[@cutabove9046]

Over load told you below in his comment that inrush current on an incandescent test lamp can exceed two amps. He is correct. Just hook up you scope for a single trigger to your test light and you''ll see the inrush current. Using a meter you only see steady state current. The only place on a pcm you should be using this type of test light is when testing powers and grounds, never on a signal input or output. Besides what does a test light tell you about those pins? Absolutely nothing! You want to test the integrity of the wires going to and from your PCM? Fine, then pull the connector from the PCM and do your testing under a real load that is presented by various bulbs used in automotive. A 2 to 3 amp bulb works well for these applications to determine if a wire can handle a load. And the point where you hook up your multi meter to your test light and tell us there is no current flow because the light isn't illuminated is not true. Of course there is current flow, but because you meter has such high impedance (resistance even on the cheap meters is 1 mega ohm) the current flow is so low it won't light the lamp. Did you forget that in the beginning you told us a meter works by measuring current and showing us voltage by internal conversion to ohm's law? So, if there wasn't any current flow you couldn't measure voltage based on your explanation. Besides, that's why you use a multi meter because the impedance of that device is so high it doesn't affect the circuit you are testing. Rethink what you presented in this video and correct it before people start blowing up their PCM.

[@joshgrieco6192]

I know its not exactly what you are talking about being a 12v short on a signal wire but I bought 2003 volkswagen that did have a ECM failure due to a short in O2 sensor wiring. It had the issue when I bought it and and although I don't know exactly what wires shorted on the O2 harness here is what i do know. All wires were worn to bare wire on original o2 sensor Codes for o2 sensor short to ground as well as throttle position signal (dbw) intermittent. Car would go into a limp mode because of the throttle angle signal Replaced o2 sensor, all is well but intermittent throttle problem persists. What I think happened was o2 heater circuit which the ecu controls through ground had shorted to unfused 12v and had burned up something in the ecu that controls the the throttle motor.

[@dimbulb330]

Maybe I missed it in your overview but I didn't hear you mention the multimeter itself. Most decent ones are 10 Meg, low end ones maybe 2, analog not much better than the test light. The body thing is easy to forget and has options as two fingers on the same hand, finger to let's say elbow, or across as you demonstrated. Good video.

[@imanewera8629]

You have a PURE Funny Heart sir. your'e not joking, but still, its funny. Thanks a lot for all your video. I believe this is a great source to learn. May the God bless you.

[@luisgonzalez8423]

What happend to this man? 3 months without a video

[@chiparooo]

Interesting video. Thanks for sharing!

[@orinmangar2333]

V=IR. Ohm's Law. Voltage=Current x Resistance. To get Current, divide voltage by resistance, and to get resistance divide voltage by current.

[@wallebo]

Wow! Great explanation. I watched it multiple times and will refer to it in the future.

[@willianandredeoliveira9737]

My favorite youtuber. Great video!

[@bernt_nielsen]

I love you channel:)...wondering if you could make some videos similar to what CarWizard is doing? Go through each car manufacturer and say which cars and trucks you would buy and which ones to stay away from? I greatly value your opinion. Cheers!

[@steffenwolffe507]

Good to know you aren't a Gynecologist. That caught me off guard. Well timed, haha!

[@christopherwietrick7911]

Classic! Thanks for sharing your knowledge and the humor is a great touch!

[@redamaleki]

Can you do a top 5 of vehicles under $10k that have 7+ seatbelts?

[@cboyamg]

Voltage can certainly destroy electronics. 24v on a 12v system is going to cause major issues. Also ive seen a test light destroy a pcm.... It wasnt a computer safe test light but ive heard that even those can do the same. You need to measure the resistance of the test light and also the resistance of your multimeter. The meter is going to have a resistance similar to the human body, s computer safe test light will be much lower and a regular test light will be the lowest.

[@fu1945.]

Thank you for another technically informed video keep up the good work... please.

[@davidmahady8241]

I'm super dumb don't get it much at all so I admire you who do !! Electrocuted would be distinct possibility for me!! Got Cobolt power steering can't seem to fix and only ones local willing to deal shorts in cars won't be cheap just bums me out I wish someone knows what they are doing could help😔😔😔

[@RJ-vb7gh]

I'm so confused now... Why not just probe both sides of the O2 sensor, start the car and see how much voltage it's putting out?

[@tonykarata9398]

It’s extremely rare when a pcm goes out but I’ve seen it done ether you lose communication with the obd 2 port or it just has a flaw that you can’t get rid of even tho you swapped part and checked the harness !!!

[@billrobertson4753]

A test light clamps to a ground, to test for hot wires. Read the instructions it tells you to connect clamp to GROUND , test probe to check for power

[@blado3442]

In 1992 or it could have been 1993 a little girl in a small town called Kosti where I lived died from a car battery. Back in the days, multimeters were not commonly available to everyone. So, what they used to do was use their tongue to test the 9v batteries, the ones for radios and cassette players. The idea was to spit on your arm place a battery right on it and then touch the positive side of the battery with your tongue if, you felt a strong tingling sensation then you knew the battery was most likely full or at least good to use for a couple more hours. As for the car batteries, you would simply attach 2 leads to a battery and strike the 2 together rapidly as if you were lighting a match if, it sparked weak the battery was either bad or very low and if the spark was nice and bright then, the battery was full and good to go. Now, the little girl's father and brotherwatching and absorbing everything.batterytongue. She dropped dead right there. Her mom saw her falling from a distance. She was 7 years old. This shook the whole city not just the little town. It was devastating. I encourage everybody to please, watch out for kids and yourselves when working on anything regardless of how dangerous it is. Aorganize things around

[@paulparoma]

I just bought a Rostra cruise control for my Scion. The instructions say using a test light may damage it and therefore only a multimeter should be used.

[@paulparoma]

@Sam S I see. Makes sense.

[@paulparoma]

@Sam S You are giving me a headache, chief.

[@bwest-yq3uc]

Where did you go?

[@Erjet1008]

Thank you, thank you, that was a great explanation! Thank you

[@satchboogyfan]

Omg I love your sense of humor

[@jsulikk]

bruuh I DIED when you joked about not being a gynocologist

[@juancabeza5809]

Thank you for not making videos about surprising your dad/mom with his/her dream car!!!...👍👍

[@garretteidson8372]

If there is a pathway to ground, doesn’t that mean that your are effectively sending 12v to a signal wire that is meant to take 2.5? The problem is that the pcm grounds the circuit, thus sending more amps than it was designed to handle. Idk man I only use a test light on 12v wires.

[@TheGrantCropper]

I unhooked the positive battery cable from my fuse box and touched the end of it to the metal part of my PCM and the car started to click and flicker and now it won't start. The fuel pump also doesn't cycle on then off like usual anymore, just stays on. Have I fried my PCM??

[@Blutnase]

Thank you my friend. I think I found a couple problems. Problem number 1. Your incandescent test light draws 270mA which means that if it were connected to a transistor which is rated for a lower maximum current, that transistor could be burned out. Such a transistor likely to be found in a PCM would be a surface mount type, which most commonly is limited to 100mA. Problem number 2. Referring to James Watts' calculation to measure power in horsepower you said that his wife weighed 550 pounds. I read the Internet and it said they traveled to France and Germany so I don't think she could weigh that much. There's no way someone that big would fit on an airplane. Happy new year!

[@squirrelkilla7371]

1:59 Bazinga!

[@HOANGUYEN-uf4vm]

My Mercedes Class A 2002 has cooling fan not work even in AC on, I just check the connection to Fan control module with a test light and see all the power is OK and the wire from ECU make the test light up and down lighting when the car running, and amazing after that the fan work perfect again ! Don't know why, maybe it resets something in ECU ???

[@johnwhite4426]

Hey! Love you channel! Very cool information.

[@JOMaMa..]

You’re the man in Sun Valley 😎

[@enriquemartinez7990]

What about the LED test light what's the difference worse than regular test light thank you again great video

[@kcee7841]

Ratchet and wrenches dude where are you? Hope you're staying safe out there 🙏 #RachetsandWrenchesDude2020

[@tecfixed2840]

That's why I use an led one, maximum of 20mA through it just to be safe, but I have never damaged or heard of anyone damaging a module with a test light and have been doing it for over 20 years! The bulb is a resistor technically so should limit any damaging current through it.

[@Pankajrana215]

My car’s O2 sensor’s wire was damaged. When i went to the SERVICE CENTRE they told me that the pcm has been damaged due to faulty O2 sensor. So they wanted me to bear the cost which i did then. But i was never sure that a faulty O2 sensor could damage the PCM. They did not cover the PCM in warranty.

[@thesakcheegii]

Mega ohm. Not the mill ohm test trough body. Resistant decrease depends on high voltage. Because of body is organic matter.

[@mostlymoparih5682]

Good video. Happy Motoring and Happy New Year.

[@isaachill89]

9:27 I thought he was fired when he stutters on 12.1v lol

[@mobilecommunicationsnetwor5268]

Are you saying putting 12v on a 5 v signal reference with the test light, the ECM will shut off to protect itself?

[@Jay.Walker]

I had my test light on negative terminal and accidentally put test light probe on postive wire. Light didn't light up. Then I tested ground on same plug in and nothing lit up. Bulb is good. Did I damage anything by my 1st mistake on plug-in positive to Battery ground?

[@justcompton]

No current flow, How does the test light shine with an open circuit?