No Start from a shorted MAP sensor (Honda, Acura)

The methods shown for testing computer power, ground and 5V reference circuits can be applied to any year/make/model out there. This is a great video on what to do when you’re faced with a no start, no communication problem. The vehicle featured also had no spark, no injection pulse or fuel pressure during testing, all of which pointed me towards an engine computer issue.
Engine Performance Diagnostics chapter 9
Symptoms
- crank no start
- no communication with ECM
Fix
- replaced shorted MAP sensor
Tests shown
- how to check for scan tool communication issues
- using the check engine light during diagnostics
- how to check the 5V reference circuit
- how to check an engine ground for a poor connection
- how to use a wiring diagram to identify computer power and ground circuits
- how to locate the correct pins on a bulk connector using wire sequencing
- verifying your scope ground for testing
- how to check computer power and ground circuits using voltage drop
- how to make sure you’re connected during ground-to-ground voltage drop checks
- understanding 5V reference circuit design
- how to check for shorted 5V reference sensors
Tools used
- Autel MS905 MaxiSys Mini Diagnostic System with Connector Kit - USA Version
www.jbtoolsales.com/autel-ms9...
- PicoScope 4425 4 Channel Standard Diagnostic Kit
www.aeswave.com/cart.php?m=aff...
- Digital Multimeter www.jbtoolsales.com/equus-332...
Playlist
- (Chapters 9, 10 and 11) The 5v Reference and Signal Circuit Quick Tests
• (Chapters 9, 10 and 11...
Related videos
- Poor running, flashing CEL, no codes (bad computer ground) - Toyota
• Poor running, flashing...
- 1996 Jeep No Start Case Study Part I
• 1996 Jeep No Start Cas...
- Bad Engine Computer Testing Part 1
• Bad Engine Computer Te...
- How to check the 5v reference circuit for a short to ground (Cadillac)
• How to check the 5v re...
For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available at www.scannerdanner.com as an eBook or paper book.
Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium www.scannerdanner.com/join-sc... There is a 14 day free trial.
On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!
Disclaimer:
Due to factors beyond the control of ScannerDanner LLC, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. ScannerDanner LLC assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. ScannerDanner LLC recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of ScannerDanner LLC, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not ScannerDanner LLC.

[@ScannerDanner]

Just some fundamental knowledge my friend. This 5v ref. circuit is the same on every car. Thanks!

[@scientist100]

I've heard you say there are cars with 8volt reference signals. Is this correct? Maybe I'm remembering pull down or up designs. Thank you for the great content.

[@ScannerDanner]

@@scientist100 yes sir, Chrysler systems from the 80s through the late 90s used a 8-9v reference for the cam, crank and vss inputs circuits, while using a separate 5v ref for the rest of the inputs

[@AutoTechHector]

Congratulations on your 2 years on KZbin ScannerDanner. i've been following you since the RX300 misfire video and been learning something new ever since. Thanks to you (your E-book, case studies, and video lectures) i've been able to fix vehicles that the "Lead Techs" haven't been able to fix. THANK YOU!...

[@mattdloughy5369]

I can't thank you enough for all your wisdom and generosity with it. It sounds crazy but a completed circuit can be applied to just about anything in life.

[@jonwally2002]

Love your videos. Just had to help another tech in my shop after he did an engine swap. Had exactly the same symptoms. He tried swapping the coil, crank and cam sensor from the old engine before I stepped in. After checking crank signal and not finding it, checked 5v reference and did not have one. Computer not so easy to back probe so started unplugging sensors. Found that in the rush of putting the engine back in, he had plugged the cam sensor connector into the coil. Unplugged the coil while watching the 5v reference, boom, 5v now. Easy fix but shows how easy it is to over look something so simple.

[@turtlezed]

I see this was 6 years ago but I am about to go and troubleshoot that exact scenario this weekend and your comment is more useful than you realise, I think you may have already cracked it for me.....I am already on a good path with this one, thanks for the 5volt input dude 😉 👍

[@jonwally2002]

@@turtlezed you’re welcome, hope you are successful

[@ScannerDanner]

Thank you Jonas! and may God bless your mind as you continue to learn in this great field.

[@liar8678]

scanner danner best teacher on youtube about car electronic ,briliant teacher.

[@ibenripped]

After spending a lot of time checking rechecking and re rechecking thinking I missed something, I come across this video that makes sense and is put in simple to understand terms. This procedure makes testing simple and quick. Thank you.

[@simbad909]

9 yrs later.. and im amazed how u do ur stuff.. a friend use to call me a jedi when i would fix his pc.. gotta pass it on....jedi👍

[@TheAdam212121]

Thank you for being clear and concise in your videos. You may have just helped me figure out where to look next.

[@PaulPhillipsFix]

Excellent video. I had a shorted TCM pulling down all com on a Mercedes I bought. You're doing a terrific job enlightening others. Thanks!

[@andrewdomenitzdmd]

Been working on my own stuff for 50 years. Way back before all this complicated stuff. Always looked for obvious first, cracked disconnected hoses and broken wires, burnt wires, chafing wires. Blown fuses, open circuits. All we had were test lights and a multimeter. Now that we have cars on the computers and can bus system it has gone way complicated, but thanks to guys like you us do it yourself types can figure it out again. Back in the day I hung out in the local garage and watched. That is no longer really possible anymore. Thanks to youtube you can hang around thousands of garages.

[@jameritch6516]

Would never have thought a shorted sensor could cause that. You guys are awesome.

[@ScannerDanner]

what a compliment. thank you very much for all your support!

[@lucasogden8619]

Very informative, excellent videos, explained well. Nice to not just hear how you do something but why you do it. Also like to see you fast forwarding in areas where it's obvious to do so because of repeated testing of certain components. Your an excellent teacher, look forward to more videos and will definitely take your advice and suggestions of tools and services available that you support that could help me become a better mechanic.

[@leviscott8519]

Great instructional video as usual Paul! You are a diagnostic genius to say the least! All your videos are so helpful and chalked full of intuition and accurate persistence! I cant thank you enough! You teaching skills are both top shelf and down to earth. independent thinker inside and out the box. A++++++++++++

[@joaojonasarendartchuk86]

Hey Paul if one day you decide to come teach in New York I will definitely be one of your students. Thanks for really teaching how to fix a problem NOT change parts. By watching your videos i decided to buy a Snap on verus pro and now feel like one of your students learning how to use and fix problems with you. Thank you very very much man. May God always keep giving you more and more understanding on how to fix and teach people.

[@XoFFoX777]

YEp ... great job and very good troubleshooting approach ... I used to do this sort of thing on a brd level at an electronics mfger where we have a test jig for a pcb and it tells us what test fails and then we find that area on the schematic and proceed from there. Golden rule of ANY electronics TSing is power supply power supply power supply ! As you were saying most electronics today are protected from short circuit and over current as well so it makes it pretty easy to track down these sorts of issue. Well done Danner

[@rithychap91]

Thank you very much for that write up (video). It was very informative and very helpful in regards to "no start" issues.

[@ShiversRSS]

Great case study as usual. Thank you very much. I love learning and being stepped through your thought process.

[@buckrogers5893]

I've seen a lot of troubleshooting videos on here this is by far the best.Your students are lucky .THANK YOU!

[@ScannerDanner]

Thank you!

[@amorozzo70]

been watching your videos,but this is the first time I write,thank you for all your videos, and this one is one of the best.

[@ScannerDanner]

i am flattered, thank you. But i am nowhere near that mans level. He is so good at what he does. I have so much respect for him. Any class John Thornton is teaching is one that I am signing up for.

[@ScannerDanner]

you are very welcome, and thank you for the comment

[@RichardFiander]

As i research and troubleshoot my Element I am starting to think that mechanics are more electricians than mechanical specialists when dealing with cars. Thanks! Your videos are great and totally make sense to a rookie under the hood.

[@InsideOfMyOwnMind]

I saw this one when it dropped and again now. Still an awesome watch.

[@bric2661]

Hey Paul, Great video you have convinced me to buy your book, all the best from the UK.

[@Amopower]

Another great video. Long time subscriber, and what you prove is that it doesn't matter what car you are working on, you dont need to be experienced with every single car out there, the concepts are fairly identical and therefore so can the troubleshooting. It almost makes me want to purposely create the faults you find, so that I can do the same tests to prove it. My luck though, I'd have the PCM without the "safety" circuitry to handle a short and would blow the PCM, lol.

[@DJDevon3]

Man what an amazing video. I learned a lot about the importance of good reference voltage and how sensors can be interconnected. Thank you. You are awesome.

[@import0408]

Omg this is by far my favorite video this is the stuff that will drive you crazy and you systematically took it on step by step

[@malisa696]

Great case study Paul. We sure have to pay attention on those shared 5V references even if they coming from two separate pins in computer.

[@donaldyocum3570]

You do t he most amazing videos. I learn so much from you. You are one of the few teachers who explains things in a way I get it. You have helped me further my career so so much. Thanks Paul ! My biggest downfall is no communication. Could you do a video on that with a can bus vehicle where a module takes down the network plz? I don't under stand how to figure out which mod i/ node is taking down. He net. Thanks for all you do. You are an amazing tech and teach! Keep up the work

[@mannyfResh1893]

I'm happy that you enjoy your job very very well and share your knowledge to the technicians who wish they had their co-workers as friendly as you are to help them. I must thank you for 1.) Selling your ebook to me in a printed form 2.) For being a teacher/instructor for all technicians who seek valuable information and testing procedures that you offer us. I greatly appreciate it. Thank you.

[@sivucit]

I have watched 1000's of videos from various authors around the world from UK, Australia etc , spend around 3000 dollar bought lot of dvd (trust me) so far, but ur ebook I bought costed just 30 dollar(not sure how much it is now) and I value that book then those 3000 dollar dvd's... u are the best so far. you know why because u are honest and humble. if the other author have this kind of knowledge like u have they would have sold for million dollar, u are a million dollar guy,

[@Atacama777]

Excellent, definitely the best learning resource on the web.

[@grosjean3]

Well done.So amazing to look at you and going stepby step and that referenced 5 volts is awesome.

[@ScannerDanner]

Thank you!

[@rrmech11]

Excellent. Paul. Love the direction

[@spierotti14]

I agree with manny mr.danner we realy appreciate you sharing your thought process! Unfortunately in the field most other technicians don't want to teach what they know because they don't want you to start getting more of that work. I rely heavily on my youtube teachers to progress in this field. Thank you very very much

[@tigerksewsankar7667]

Thank Paul for explaining the 5 v reg great job man thank you sir.

[@AutoTechHector]

This is the kind of issue that would have this vehicle jumping from shop to shop with dozens of parts thrown at it..Very few techs would have figured this one out. You're just that damn good man!!

[@JoelAutomotiveInaction]

this is another great video always some thing to learn, good lesson Paul thank you . the best teacher I ever seen. your book is amazing

[@redsson6669]

excellent video paul i think between just these last 2 videos/ they cover all steps approaching any no-start condition.

[@ScannerDanner]

for sure it seems like it would be a great addition to the diagnostic tool box for that type of testing.

[@benji1990x]

I'm addicted to these videos just getting the hang of 5v references unplugging and reconnecting sensors I've ordered a snap on d8 triton was a trade in so got a deal on it now I'm going to start practicing using a scope and values still got a long way to go yet as I'm just starting but your videos are priceless

[@ScannerDanner]

Thank you! When you're ready, join my classes I offer via my website. I have over 400 hours of training material, from classroom lessons recorded at the technical college i teach at, to exclusive case studies. Hope to see you there! www.scannerdanner.com/join-scannerdanner-premium.html

[@GRUSSNewton]

I wish we had Mitchell on demand wiring diagrams in the uk! Great video by a great teacher!

[@Mulletsrokkify]

A superb logical approach. Another fault finding gem. Thanks for posting this.

[@naushadali95]

the best teacher in the world.you are brilliant sir

[@rickchapman3707]

This is one of my favorite videos really enjoyed this one!!

[@kalindambozi2356]

My best lecturer. Always wish i knew you earlier. Am learning alot. Thanks.

[@ScannerDanner]

Love this comment. Thank you

[@timothyddibabisasso7109]

Thanks for the great job of making us great technicians

[@warphace]

Bravo, that is troubleshooting on another level. Great lesson.

[@benrodeheaver701]

So glad I found your vid ! Changed engine in an altima and same woes. The maf is the only thing I haven't unplugged trying to start w/ no spark. Hope it does it. Thanks.

[@nestorfresno1]

Hey Paul great test, i agree checking for voltage references from pcm when you dont have communication the first step, test is to verify what the pcm need to supply, which is voltage 5v references ,totally agree,, thanks for sharing

[@demontuning5512]

Lord of the 5V Reference Circuits. Good lesson.

[@paul06660]

That is an awesome diagnostic video for someone who is not quite familiar with this situation. But early on in the video I could have told you that the plugs for the map and tps were mismatched. Happens most the time when someone is not careful in their engine swap and hooks them up wrong because they both use the same exact plug.

[@jarinwilson9539]

why should you check for a good 5v Reference? Remember, the 5v-ref. circuit is an output signal from the module used for diagnostic purposes/feedback on wiring integrity. If this is not present, this indicates that the module is not awake. I've seen 7v-ref circuits, 10v-ref circuits etc, but 5volt reference circuits are the most common amongst vehicles, at least from my experience. Awesome video, I thoroughly enjoyed it

[@scannertz6505]

Thank you, sir. Really helpful. Great lesson

[@MitchMartinEngineer]

Good stuff Paul! I love the technical side you bring to fixing vehicles, and also the knowledge you bring. My "subscription" to your channel brings much more than most any other channels out there. I subscribed because I like learning, and also because you're a damn good teacher. For that, I thank you!

[@johnmckamy6398]

what an excellent video, extremely good information for going after a no start .

[@ScannerDanner]

Thanks John

[@tnamen1307]

@@ScannerDanner one confusion....the 5 v reference signal is shared to all sensors. Now, if the 5v signal to MAF is shorted, why the engine can start with the MAF sensor unplugged?? Is not that the ECM will not provide any signal to other sensors too? Please kindly brief clarify. Thanks.

[@ScannerDanner]

@@tnamen1307 key word "signal", a 5v signal wire on a digital MAF like on a GM, is a pull-down type of circuit. The computer sends 5v to the MAF and the MAF pulls it down to create a digital square wave pattern. This is NOT the 5v reference circuit. Yes, it is tapped into the 5v ref inside of the engine computer, but it is isolated by a current limiting resistor. In short, a 5v signal wire is totally different than a 5v reference wire. Hope that answered your question.

[@tnamen1307]

@@ScannerDanner that means, if any sensor or wire sharing a 5 v reference circuit or wire is shorted, then all the respective sensors will not work. Is this my understanding correct??

[@tnamen1307]

@@ScannerDanner and, another question relating to ac compressor. My car i20 engine is running very quiet as usual. However, as soon as AC clutch is engaged, I hear a squeak sounds and not metallic sounds or alike. The squeezing like sounds go away immediately as AC is off. Even with engine revs, same sounds. And with AC off, as I revs the engine, still the engine is quiet. How to find that squeaky like sounds and fix it? The AC is blowing cold. It seems the AC compressor is ok.

[@mikembz1]

Paul i believe God all mighty send you to earth so you can teach us this a gift.thank you sir.

[@alabalanutnbolt]

another really good video. spot on with the method paul. learn along with danner is better than factory training.

[@christopherreynolds8247]

Wow this is so sweet you are so good in what you do i keep looking at this video over an over very nice.

[@HayesMobileAutoRepair]

thank you, this info was a huge help...the sensor did knock off my check ingine light and no start condition... anyway, all is good now..the computer was getting very hot during all my checking but now the fuel relay is malfunctioning and will not start normally... but it will start if I supply voltage to fuel pump... anyway, Ill look at it tomorrow.. thanks again..your awesome.

[@billrimmer5596]

Fantastic video! Use this info all the time.

[@nestorfresno1]

very good testing procedure diagnostic flow chart.thankyou for sharing we always learn somethign from you....

[@fivefortyeye540i]

Luv theses type of case studies, great for dirrection base.. GURU!!!

[@tunespt]

Thanks for the awesome video and information! It really does help to get things fixed faster, mechanics are starting to hate me :D

[@dobroiuflorincristian4706]

omg ..so much to learn from you...and this video have 10 years

[@ScannerDanner]

Still just as relevant today my friend. Thank you!

[@FettManTAG]

I notice that the odometer reads 141,693 miles even though the engine was swapped out. Could that be a sign of the computer not being able to communicate with the engine? Every time you solve the issue I'm simply blown away. Thank you for the work you do and the effort you put behind these case studies.

[@martinguitarhd28]

I learned so much from this video.Thank you

[@ScannerDanner]

+martinguitarhd28 thank you! I have so many more. Thanks for watching

[@subaru733]

thank you i have been working on a 2006 subaru wrx no power to the pcm no power to fuel pump no power to injectors and i just went in to work and unpluged the maf and it started right up thank you

[@TheOvnicar]

very good video amigo paul

[@michaelpearce8661]

Awesum videos you make and yes I spell awesome differently than most people. I have my own reasons for doing it. Some = a few Sum = total. Awesum total amazement. Seems logical to me. Really liked your video, thank you for your time and what a gift to share with us.

[@MrBeauxellis]

Killer! That was awesome, thank you for the demonstration.

[@cloud8056]

very good presentation on ref. voltage,and seeing if computer is alive.

[@danielm.8301]

I I

[@maggiereyes2903]

Once again dan the Man....super Awsome Knowledge...Almost Master YODA Status...Great stufff Keep the Knowledge a coming...Thanks U a Bunch...U dont Even know how much u just helped me out...Dan the Man!!!

[@InsideOfMyOwnMind]

"There is no try. There is only do."

[@alexsenicynlv6563]

Thank you! very good,very instructive video

[@nickayivor8432]

Good Evening Sir ScannerDanner take care and have a great day Sir ScannerDanner Thank you tutorial great 👍 👌 From Nick Ayivor from London England UK 🇬🇧

[@ozzstars_cars]

Amazing how sensitive the computer is missing just a few volts which can cause big problems. Great vid once again, thanks!

[@manuel7958]

Some great great stuff you got there Thank you

[@markhamill5307]

Another great video thanks again Dan Mark

[@albertomendoza9565]

Gracias, gracias, gracias!!! Straight to the point, and clear as daylight explaning. ✌😎 New sub. Stay 💪. Thank you very much.

[@ScannerDanner]

Thank you so much! And welcome to my channel

[@stanleymorton2992]

Great job of troubleshooting.

[@efrencerda5459]

Great case study,., thanks Paul,.,.

[@Altermyego-]

Awesome video actually all your videos are awesome - I'm experiencing similar symptoms and after watching this I'm fairly convinced and hopeful that my issue will be the same. I've already gone through the ignition coil module OPTi spark you name it thank you

[@ScannerDanner]

+Kevin cool. Let me know if you fix it

[@Altermyego-]

+ScannerDanner Thank you so much for your reply... You're truly an amazing technician and a selfless person to share your knowledge and experience, especially at the level of educating others for free. • on my 94 Z28 5.7 L, i took it to an (alleged ASE tech) to work on my vehicle, which I literally never do ever. ( in lieu of my depression & severe anxiety disorder) - "intermittent stalls and no starts" The asshole - "oh, its the opti- $900. Immediately after leaving the shop I go to the car wash & when I try to start the car after washing it, crank no start! "exact same symptoms as when I took it to him. I'm so fucking angry I cant figure out how I'm going to handle this. I did call him right after it wouldn't start of course he didn't answer, it was 20 minutes till close -voicemail: me: " I'm leaving my car up there exact same symptoms"...

[@johnavila7942]

Another simple video that is understood

[@princeclive1913]

Paul danner is the greatest teacher in the u tube there is no point putting tumb down... Mabe those who put their tumb down are those who don't understand or jelouse of his brilliance... Next time if you don't like his teaching you may fuck off without any comments I learned a lot from you Paul thank you ...CLIVE from Malaysia...

[@ScannerDanner]

lol thanks man

[@ScannerDanner]

I'm not but thank you Hector! You made my evening.

[@hectorvigueria378]

60 ur. Old man and I love to work on cars engines .I always avoided eiectrial repair or troubleshoot but now I've so much off of his videos he makes it look. Easy and interesting scanner Danner day shit!!

[@tigerksewsankar7667]

Sanner D you are the man thank you.

[@ScannerDanner]

I have not. I have seen the tool and it is pretty neat. I prefer loaded circuit voltage drop testing myself. I understand there is a need to unplug a circuit to test it at times and this tool could be handy for that.

[@Shamus71]

I have a friend with an 05 Dodge Ram 1500 van who is having a similar issue as what you had going on here. It's an intermittent crank but no start, and "no bus" clearly indicated on the cluster, and no data link while this happens. This weekend we will be looking it over. He assumed possibly a bad crank angle sensor, I told him to watch this video since something is possibly grounding out the reference circuit.

[@MrOscar442cutlass]

Probabky bad ecm

[@1979jwm32]

Excellent video. Thanks.

[@TheWaelabo02]

thank for teatch us realy you do very good job .i learn from you to much and steel more thank you

[@shopyard87]

Great. When u checking power and grounds, r u having d key on engine off?

[@alrifainidal]

awesome work . you are amazing

[@CoreyRaines]

Well done Sir.

[@tigerksewsankar7667]

May God always bless you sir thank you.

[@stevescott8758]

Great case study 👍

[@ScannerDanner]

Thanks Steve!

[@BrettyUK]

I've ordered a set mainly for testing lighting circuits on trucks and trailers. Handy for this as you need a hell of a jumper cable when your 40ft away from the batts haha.

[@dblr616]

The next time this car is a no start im gonna go out on a limb and say it will be the never start battery, i love walmart but hate there batteries;) Thanks for the amazing videos Paul.