Audi P0638, PWM/Duty cycle explained 

Fantastic video as usual Dan!

I am a master technician here at the Jersey shore, USA. I enjoy watching your videos as I use them as refresher courses for myself. Having been in the industry 40 years you tend to forget things you don’t utilize on a day today basis. Thank you for what you do. Keep up the good work. Have you ever thought about bringing your show on the road?

some day I hope to graduate from Diagnose Dan RU-vid University. And that day all the credit will be yours Dan. Bless you.

These are the best videos on RU-vid if you really want to no about automotive electronics

Really really impressed by these videos Dan. Have been in the motor trade for many years, have been on many courses over that time and I really don’t think I have experienced the simplicity of how you explain how automotive systems work before! Really grateful for these videos. Please keep them coming. I’m sure great things will come for you. Very good work.

Can we have your backstory. How you got started, what exactly you do, did you go to school, tour of your shop, etc. awesome videos. Thanks for the time and knowledge!!

Nice belt professor! 🙂 Another great video! You make it so easy to understand, you've got a real talent! Thank you so much for the videos,I wish you'd post more often but I'll take whatever I can get! 👍👍👍👍👍👍👍👍

You don’t find many people who are as capable as dan. I would like to know where he is working. I have been laughing how many BMWs seem to be having awkward problems, that others can’t fix. Then you go ahead and show what has gone wrong with ease.

Diagnostic Dan on 90% of VW/Audi diesel engines by design the flap motors go bad because of how they are installed , meaning they have the electronic box on the flap motors are directed downwards and all the condensation from the exhaust gases is eventually leaking by the flap shaft in the electronic part shorting the thing , bad design that's all

Getting the basics right from the start, such as the function of the throttle body on a diesel engine, has serious implications down the line where correct diagnosis is concerned. Pwm is given the complete teardown with some very interesting practical applications, demonstrated. The advantage of using a scope from this and other videos, cannot be overstated. Very informative video and so well presented.

Dear Dan, thank you so much for your videos. They are phenomenal and you are the best teacher I have come across in my life - believe me I have had many. I myself used to teach math and physics to high school students years ago and knew I was not a good teacher, but did not know why. I quit after five years of teaching. I liked tinkering with machines, love cars, had a degree in EE and fixing stuff is rewarding, so I decided to become a car mechanic. Watching you present your "lessons" really opens my eyes to better see what I lacked as a teacher. It is what you abundantly have - good understanding, broad knowledge, apparently a lot of experience, good teachers who taught you well, and a gift to communicate humbly what you know and do best. That gift is extremely rare! I hope you and your family stay in good health, your business thrives, and you continue to teach us. We are all eyes and ears-:). God bless you!

That was great. I'm an electronics engineer and computer scientist and have even built RC Airplane with (PWM) servos and controlled them with microcontrollers, etc., so I understand PWM just fine, but it was super helpful to see the tools you use on a car to figure out what's actually going on. Also your PWM explanation was really clear.

My coworker had the same issue / code with a TDI back in May. He fixed the car... but did not explain things as well as you! =)

btw could you give me advice ? my bmw m54 has been working on rich condition for unknown period of time. i restored and swapped everything that could cause a problem. now my fuel trims in both banks are 0 or - 0.75. googd compression, no oil consumprion, sparks became more natural color. but i notice blackness behind exaust, seems like unburned fuel. but my wifes m54 had +8 % lean condition and her exaust is clean like new. what should i look for ?

You explain better than anyone I’ve come across. Im a car and electronics enthusiast and totally hooked on your videos and can’t stop soaking up the knowledge! Just one question, any idea why the electronics in that throttle body fried? Could there still be an underlying problem that may eventually fry the new throttle body? Just wondering if there’s a way to test for that... Keep up the amazing work of sharing your knowledge and expertise with the world 👍

Great video dan, I think alot of techs in the industry need to know about pulse width signals as most of the components in cars are using them; you have very good way of explaining things.

Great video dan. You are one of the best channels on yt. Keep up the good work!

I might buy an Audi so I have something to fix. lol Great job with the video my man Dan!

Great video. How many diagnosis machines have you got? Do you prefer one to another? Did you figure out where the coolant was going! Dermot

I have to watch videos like this many times too absorb the info. I recently fixed a 2011 Transit Connect auto trans. It has a 6 solenoid valve body. 2 solenoids on/off and 4 pwm. Does it hurt a pwm solenoid like this or a fuel injector to put 12 volts to it? I am thinking that u may damage a fuel injector giving it a full 12 volts for too long.

Thanks Dan for instructing us on diesel throttle body. Like the look of versus edge is that the built in wiring diagrams u showed, cheers my friend, Sandy

I wish you could be cloned so every workshop would be populated vy your copy :) Awesome videos! I think you should open a diagnostics school.

Hi what’s difference between that and adjustable resistance by dimming down and up ?

Great Information, Thank You.

At 1st I was a little annoyed how you over explained PWM & Duty Cycle, but as you continued I realized that you are giving "real world" explicit instruction. I have subscribed to your channel. Thank you!

so u could have just opened up the valve and seen that its blown out LoL

How comes the PCB fried? Too much mechanical resistance from carbon buildup inside the TB?

DIAGNOSE DAN, can you explain and make a youtube video going over which car components, car modules, car sensors you would measure the PWM , duty cycle and frequency? Can you list a bunch of examples please?

I'm a subscriber for life. :) Another great video. You, Eric O, and Ivan are killing me! My brain can only hold so much. You guys fill it to overfull, all of the time. Thanks.

Good instructive video as always , thank you Dan , I would like to work for free for you just to learn from you

Hi DD, I wonder why the throttlebody and the EGR-Valve are turning closed again when they are opened with PWM. The Polarity of the motor is not changed. Why is it rotating backwards to close position again? Is it a motor or something else driving the EGR Valve and throttlebody?

Very nice video, a question what's the difference between this and stepper motors?

In theory, would throtle body be capable to prevent a diesel runaway if that should happen?

Thank you for yours video ! Your are the best ;-)

Greetings from Portugal. Leon (bodgit and leggit) was not lying... You Sir are a genius. I love the detailed explanations. Thanks.

I'm not very knowledgeable on electrical stuff, but I always thought they used resistors to vary motor speeds like blower motors. Last I knew, brakelight bulbs had 2 elements. Back in my day working on my cars, they were an 1157, but I think that number was superseded at some point. Did they lose the double element bulbs and go to this pwb type of bulb? I've had a Peugeot 505 turbodiesel, underpowered as all French cars, and a Mercedes 300d turbodiesel. I never knew the throttle was fully open on a diesel while running but closed on shutoff. Interesting video, Curious Dan.

You really know your stuff i wonder. If you paid monthly for sure track on your snap on tool

I'm having problem fixing a 2006 hummer h3 3.5l engine with rough idling after overhauling the engine Replaced the throttle body still no improvement. I Keep getting power reduced massage.

Wow, it is an excellent video for complete learning of the nature of PWM signal. Thanks indeed,sir.

great video dan . with tina turner playing in the background at the end i thought maybe you'd bust some moves lol

I have the same problem p0638 bought a new throttel but after a while returned the same mistake p0638 I doubt the gas pedal potontiometer My car is Renault Campus 1.2 16v 2014 Thanks

Dan, you are amazing! There’s just one thing I don’t understand and that is, why does anyone ever give your videos a thumbs down! Thanks for sharing your vast knowledge with us, I wish I could come and work alongside you!

I would appreciate it because you are a good professional, it is difficult for me to translate with Google 👍🇪🇸

Great lessons,but I am six months behind class....

Loving that explanation. I recently had a 11 Honda Fit with a bad throttle actuator pedal. I was able to use my PWM generator to activate the throttle body. But I messed up and replaced the throttle body first, not trusting myself. I then replaced the pedal and fixed the car. If DD was over my shoulder, I would have fixed it right the first time. Diagnose Bill messed it up again!!😩😩😩

Hi dan i have 2005 skoda Octavia 1 kombi with 1.6 petrol engine . The fuel economy is really low.i recently changed lambda sensor,all spark plugs and ignition cables. Cleaned the throttle body and everything. The car has done 1,90,000 kms . But i get 13-14 ltrs in city and 9-10 on highway. Please suggest me something. Hoping for a reply from you.

Great explanation and use of visuals! Thanks again for another super video.

Alright ..... So the pcm is not controlling direct power to throttle body, it is just sending a pwm signal to throttle body, which is a fixed frequency varying pulse width type... The power(12 volt) is actually going constantly to throttle body but sometime it is turning on/ off, that's it... & On the side side there is a feedback line which should be same as that of the input own signal from pcm I guess.. Thankyou Now I have watched this video more than 2 times & everyone I watch this I feel.... Hmm, it was new, so much to learn from it Thanks for the upload Am I right..

Hey which program do you use for the electric diagrams ?

Fantastic.....just one question...do you know how the feedback circuit is responding to pcm? M talking about feedback ckt of throttle body....i mean is the feedback signal in the form of voltage or pwm it self???

Very clear explanation along with detailed. I'm loving the videos.

Great information dan, just wounder how to preform pwm test terminations , where the negative side of the pwm tester would go

Hi my car problem is 2014 Toyota Sienna a/c

Great Video. If you have a volt meter on something and your getting like 8 volts, don't assume you have a voltage drop. Flip the volt meter to duty / Hertz and verify it's not under PCM control. Communication is giving and receiving but a signal is an output to a transistor that acts as a high speed relay. That's how I learned it from scanner Danner. Lol

Very informative excellent,Thanks for your time,

I just subscribe your channel, you making absolutely fantastic videos, making complicaded stuff simple, I'm a big fan

Learning everyday,that's super delicious 😋. Thanks Dan. My best channel everyday!

Sir you are Johan Cruyff of diagnostics you are one of the best teacher your teaching technique are so amazing and simple that even person like me which i am not very smart can understand.

Thanks Dan. I have a prob with an Audi A4 1.8T 2005. MIL on. P17511 - B1S1 O2 heater performance too low. O2 heater is drawing 1.5a during on cycle. About 50% duty cycle but still throwing code. Seen this before? I have traces etc.

Hi Dan. I came across your channel during lockdown and I'm hooked. You are a most excellent teacher. My Vivaro 2.5 cdti van just stopped revving above 2000rpm and the cooling fans also dont seem to come on. The exhaust is leaving black soot stains on the rear bumper. I watched one of your videos that dealt with the reving problem and fans not coming on but i cant remember which episode it was. Can you remeber which one please? Keep up the good work and well done for training the kids too,

Super video Dan! And thanks for all of your videos.

Btw: any videos on scope operation would really help, I’m using an Autel MaxiSys 908 with the MaxiScope add-on

Fantastic video Dan! Explained as alphabet in Sesame Street. Now my 6yo son understands PWM ;) Shame there is not "Love it!" button xD

When my VW Golf DSG goes wrong I will put it on a trailer, hitch that to my 1992 Mercedes diesel which will never go wrong, and tow the Golf over from England to Holland for Dan to fix! It will be cheaper than paying three garages here to get it wrong. Hooray!

I was just looking yesterday to see if my notification bell was broken. Because I haven't seen a new video in a few weeks...only to be surprised this morning. YAY.. Thanks Dan, apparently you fixed my bell again. (: Cheers

wonderful!!! simple to understand your explanations.... thanks you

Great video my friend. My question is how can a multimeter display dutycycle/ frequency but on the regular voltage setting it cant show a pulsed votage signal it just displays the average of the signal. Everyone says its to slow to show that fast of signal but then you put it on duty cycle and it shows it. Could you please explain if you know please. Thanks for all the great lessons

this guy should really appears in automotive textbook. he is so good at teaching

Please could RU-vid place subtitules in spanish?

Great lesson. In the early 1980's I went to the salvage yard for a used battery for a car I was selling . I brought a load tester . They all laughed at me . The guy goes over to the pile with a tire iron . If you got a BIG SPARK , the battery was good . If a small spark or no spark , the battery was bad . Maybe you could use an extra " technician " ?

Thanks Dan. Your videos have taught me a lot about auto repair.Since I came across your channel I've seen things in a different perspective.Can you please help me with one of your old scan tool?Am a mechanic in Kenya and struggling to have one.

Don't forget EGR valves are designed to DE-TUNE engines by re-burning waste ...

Hello mate, nice job.. love the detail and method in your videos.. New Subscriber! Is the (Ryantool) analogue or digital? For demonstration, can u use old style coil potentiometer?

Can you please give me of the past number of the tools

That looks close to a potentiometer used on older Mercedes which has its share of issues, I have SEEN Victor from NY repair them and also the wiring harnesses Dan, check VSANDVS channel, great MB mechanic

LIN is used When the throttle body is giving the ecu the feedback about its current location, correct?

A bit late to the party, but this is... interesting. Learnt something too. Thank you for putting this video up, you're very good. I can easily follow you even though I've got a hearing problem and have to use hearing aids. There are times when there's a definite echo (especially when you face the camera in the workshop and the sound echoes) but I still can follow. Will recommend this channel most definitely to other guys and girls wanting to know more. And, as usual, eyeballs trumps scopes and testers when it comes to taking a visual inspection at the part(s) either inside or outside.

Thanks dan...once again you put accross an easy to understand lesson...

Great video Dan! How much do you pay for the wiring diagram program? I already have a lot of diagnostic equipment its just hard to get wiring diagrams for me. Groeten uit Zwolle

I think one thumb up is not enough at all, you deserve more.....thanks

I had a question Dan I want to purchase a BMW X5 or X6 for my wife which one do you recommend the most reliable

Although not mentioned I assume the throttle working correctly 'fixed' the EGR 'fault' too by letting the correct amount of air through?

You are soooooo good! I learn so much from you! Thank you!

All your video's are great training aids and can always get useful information to learn and grown

I have been selling tools for 34 years. I have worked with some of the best techs in the nation. Rod Flores probablly the best ford driveability guy in the nation. But you my friend are amazing. IVe seen you find things that what ive seen no other shop had the patience to fix, especially on bmws. But get away from that snap on crap and get some more launch and autel stuff. Snap on sucks. I was a top snap on dealer 17 years. They do not take care of there dealers or customers.

Brilliant Dan thanks again. Please can we have your Range set up when you scope for your signals? We saw from the video your time rate was 100ms your voltage range was 12v so where did you place your probe leads to get your signal? One was on the signal wire in and out and you had your ground lead connected exactly where. thanks.

just discovered your channel , briliantly done ,learnt so much just watching a few of your vids . thankyou for your time .

These videos are amazing!! Your explanations are so clear and easy to understand. Does your new ddtsb website similar content?? Great Video!

Can somebody explain, why is the pwm voltage go under 0 volts? Doesn't that mean it pulls back the valve instead of pushing it out?

Dan your videos and teaching technique are awesome! Thanks for taking time to make the videos!

So, the throttle body control module has a fried (overheated) item, which failed (prematurely) and rendered the throttle body useless ? Luckily, the throttle body stays in open position when useless ! The reliability of a brand (Audi) then depends on the reliability of its electronic components !!

The smoke in an IC is the secret to why they work and when you let the smoke out of an IC it stops working. As this IC has burnt a hole in it letting it's secret smoke out it stopped working the valve body. LOL. Another great video Dan. Years ago only a electronics techs worked with this type of equipment. Now days that skill is being lost in that field as everything in that area is board replaceable and nobody trouble shoots to component level anymore. But in the automotive world now the auto techs must know more that the electronic techs of today. Funny how things change.

Wow PWM signal. I like the way you explain and simplify the Pulse width Modulation signal and the duty cycle

Very clear explanation Dan..I like your style.. Thankyou

Hi Dan just a quick question, I noticed on the egr when you were increasing the duty cycle, the valve opened. However it fully opened long before the duty cycle was at 100%. Does this mean that for some fully functioning components we may never need a duty cycle of 100%?

Ooo! Very good light of education. Thanks!

am @ TEXAS H town, yovr vids are very informative and knowledgeable- ok men keep vp the good work; and knowledge is not knowledge if its not share !

Excellent diagnoses Dan. This explanation was great. Cheers my friend.👍👍

Awesome vid !! Greetings from Spain. THANKS!

All your videos are super 👌👌👌 How you get the duty cycle data on your laptop