Finding CAN Bus Faults With Multimeter | CAN Bus Diagnostics | Mechanic Mindset

[@sollykhan2385]

Another useful tutorial, Thanks for all the content Darren, hope your keeping well, and please keep on posting. 🙂👍

[@Yulian.Mladenov]

All videos about can-bus are really great and true! Very good job,short videos which exactly the things from the real world.

[@MechanicMindset]

Glad you’re enjoying them!

[@mechanicmatt871]

A lot of good info here, showing what can be achieved with a multimeter. Thanks Matt

[@MechanicMindset]

Good for convenience! Cheers 👍

[@CarsExposed]

Very interesting test with the multimeter there mate going to watch part 1 now 🤗👍👍👍

[@MechanicMindset]

Cheers, scope is number one but the multimeter wins for convenience - and most people can use it fine! Check out the video on CAN resistance check too if you haven’t already. Thanks! 👍

[@alihankorkmaz4350]

Hi quick question. Should all the can low and can high lines have continuity separately till the OBD port? So if I am to connect to can high wire at the steering control module and connect to can high wire at the obd port should there be continuity? Thanks

[@MechanicMindset]

Good question. It depends on the network. Some OBD CAN connects to the gateway and nothing else. Best check your wiring diagram 👍

[@ateshnarayan9769]

Good explanation. Really appreciate your time and effort used

[@MechanicMindset]

Thanks for watching, glad you enjoyed the video!

[@yofimee883]

Thank you for the great practical explanations

[@MechanicMindset]

yofi mee Happy you’re enjoying the channel!👍

[@TheGibby3340]

Good overview of the possible scenarios...Thx & Cheers

[@MechanicMindset]

TheGibby3340 Cheers, glad you enjoyed it!

[@vicky-nc3to]

So CAN high & low have a resistor between them... A fault in one side will effect to other side as well.. what rating of fuse did you use while you shorted the lines ? Thanks ..

[@MechanicMindset]

Yes pretty much; for high speed CAN that is. On low speed CAN, it’s a little different. It can work in single wire mode. I just put a 5A fuse in the jump wire; just incase I hit a ground. It saves the ground and stops sparks flying! 😂

[@vicky-nc3to]

@@MechanicMindset Thanks, it helps a lot to learn about these network system. Please keep uploading such videos as the videos available in internet are not very much helpful if you are from mechanical background, your video gives better idea of learning stuffs for a guy like me.

[@MechanicMindset]

vicky singh Thanks for the feedback; happy they are helping! More to come 👍

[@panikognito460]

Hi, can I apply this to ma Land Rover Discovery 3 (LR3) 2005 for diagnosis Parking distance aid module, it is using MS CAN, medium speed CAN bus ?

[@Valmo2379]

Hi, i'm currently having an issue with a BMW E46 320CD. Since you are knowledeable on the topic maybe you could lead me on the diagnosis. I tried the DDE resistance check and i have 121 ohms, so the DDE seems OK. On the DDE plug that connects the two CAN bus wires i also got 120 ohms. so not the terminal resistors then. I checked the canbus on the plug connecting to the instrument cluster and got around 60 ohms. Both resistors are then connected and overall resistance is within expected specifications. However, when i check the can bus plug to the light control module, i get 8 ohms ! so that tells me that somewhere, both wires are shorted together ? Seems to be confirmed when i check both CAN bus wires voltage to ground : i get 2.42 volts on each one. That would explain why i have communication problems. The strange part is that i get that resistance only on this part of the circuit. There's also CAN BUS wires going to the headlights, and i also get 8 ohms between each. All modules seems fine, when i connect INPA i can access all modules and read the digital and analog values. Thats tells me that the DDE, the instrument Cluster, the steering wheel buttons, DSC and steering angle sensors are OK. INPA tells me that the error codes relates to a CAN BUS Timeout. I suspect that both CAN wires are shorted on the lighting network, but sometimes the communication is intermintenttly restored. I had this issue in the past and replaced the DDE, which solved the problem. However, this time, the DDE seems OK. Any insight on this doc ?

[@littlemadness221990]

Is there any chance to indicate a good software for all of the electrical diagrams?

[@MechanicMindset]

I think Hella and AllData are popular options. AllData do a per car subscription in the US

[@pgmilasinovic]

Hello, i have can high shorted to ground but only while driving so it messes up the car and makes it really hard to diagnose when stoped. Do you have any video where you explain how i could trace this can hight to ground location to fix it ?

[@MechanicMindset]

To locate a problem like this (short), it’s about elimination. Especially difficult when it’s intermittent. You’ve confirmed the problem, you’re halfway there!

[@spanthefestaman]

I'm not a diagnostic technician is there an earth on the can bus wiring or just a can low and can high?

[@michaelandrade1213]

This is exelwmt thankyou

[@mahenderraj9499]

While ignition on your checking? If car is sleeping mode then how much voltage will get in chassis can

[@MechanicMindset]

mahender raj Hi, should be 0V on both: see part one of this video! 👍

[@gbush1620]

Thx for the video and guidance. I have an issue on my Mercedes Canbus "checklamp error". I replaced the set of wiring inside the front headlamp housing and used thicker wire for Parking light. While turning on parking light (H6W spec), it return dashboard error. Am I wrong doing for "thicker" wire which corresponding less heat and resistance? Regardless Bosch Halogen(6W)/LED with Canbus correction, it returns this error message. I have ordered Philips 5W Canbus Resistor from Amazon, yet arrived. Should this help to fix the issue? Please advice and thanks again.

[@MechanicMindset]

Hi, I think there is a confusion between CAN Bus and ‘cold bulb monitoring’. CAN bus doesn’t really have anything to do with normal lights. If your car returns a lamp error, it because of a fault in the circuit or the LED light you have fitted.

[@chubbychequer1512]

Hi m8 where do I get a good.set of back probes from. Thanks

[@MechanicMindset]

Hi, I have a link in the description to some Hantek ones, they are similar to my Pico ones where you can replace the pins. There are quite a few at varying prices on Amazon 👍

[@JoeBob79569]

Going to have to watch this a few times. I got a bit confused about when you were testing and when you were intentionally shorting wires together. I initially thought you were shorting the wires together as part of the test until I realised that this was just you "creating the fault". It might have been clearer if you had hidden the footage when creating the faults, but then again I suppose that in itself is instructional too. It just took my brain a while to figure out what was going on! Maybe showing a quick simple diagram on screen of the type of fault could have made it clearer what was happening.

[@MechanicMindset]

6 minutes is a tall order to cover this off! Check out my 4th and 5th video where I use a scope to diagnose the same faults, and show you how CAN is connected with the resistors etc. 👍

[@JoeBob79569]

@@MechanicMindset Yea, I understand the concepts and all, with the terminating resistors, etc. I just meant that it would be a bit confusing for somebody following along, and not paying 100% attention, and then they go out to their car to diagnose it, but instead they follow this procedure (exactly) and they short the wires, and then measure it and find a short in the wires, and think their can bus is shorted out! If that makes sense? But yes, I'll definitely watch the other videos. I think I've got the basics pretty much down, but I'm just watching a bunch of different videos to make sure all the concepts are solidified in my head. I'm trying to diagnose a consistently random intermittent fault in my high can wire at the moment on my X-Type, between the TCM and ABS. I've got a Hantek 6022be in the post so it should be here in a few days, hopefully it will make the process easier, seeing what's going on with the signal. It's a strange one, the car is running fine, and almost all the values are fine on the diagnostic (speed, amps, etc), but it jerks when putting it into gear, as if the car isn't getting some reading correctly, like a crankshaft torque/speed value or something. And I get a U0001 communication error that comes back 10-30 seconds after I clear it.

[@eglentgjoni9947]

Yeah bro I really like videos like this and your time spent for this video, What do you think about 10v Can H and can L about 10v as well? I've unplugged about 95% of modules and wiring but no change. The initial problem is no drivers window and aircon. Got this car from main dealer. Any advice appreciated

[@MechanicMindset]

@@eglentgjoni9947 Could be a resistive short to power. A look at the oscilloscope waveform will give a good idea. I take it there are no comms with any modules?

[@eglentgjoni9947]

@@MechanicMindset that would have been great if no coms with any module, that's the start point wright there. But I have coms with every module!!!! I've chopped the rear end off the car from the front and still have 10v from front or rear independently. What is going on??? I'm being doing this for the last 20 years

[@stephanevaucelles6378]

thanks for video

[@MechanicMindset]

Thanks for watching!

[@harshnegi985]

Whenever i honk the source changes .I have got the mouth of system replaced but to no use.Can this be because of faulty canbus please help

[@MechanicMindset]

Sorry not sure

[@vick9333]

How do I isolate damaged module?

[@MechanicMindset]

Disconnect and reconnect them one by one to find the problem 👍

[@jamesbarratt593]

Car wont start and scan obd no modules show up. Yet the modules seem to all work except ECU. What reasons are there that autel im608 pro and autel maxisys cant see any modules.

[@MechanicMindset]

It depends a lot on the car. Gateway connection?

[@jamesbarratt593]

@@MechanicMindset vectra 2009. Breakout flashing blue pin 6 and 14 and all things seem to work. Wont crank or run and no comms but no engine management symbol either. Plan to check resistence of can lines. Can I check between obd and the engine computer to see less than an ohm?

[@jamesbarratt593]

@@MechanicMindset what is can bus gateway

[@MechanicMindset]

@@jamesbarratt593 Check out this video mate: kzbin.info/www/bejne/oWnFe5idi92ilcU If you still have questions, I would advise joining Mechanic Mindset Diagnostic Coach (only $10/mo). We’ve got a full CAN Bus and Networks course with downloads and activities 👍

[@geoff3172]

Has anyone managed to hack the pico compression and battery software so it can be used with the 2204....

[@MechanicMindset]

Geoff not as far as I’m aware

[@orlando8193]

Sorry mister, My car(panda fiat 1100cc 169 model, 187 engine model) I have can line to short circuit to positive.. Obd2 diagnostic pin 14 only key on have a 12v, battery tension to ..pin pin 4 or 5 ground... Pin 6 have 0,3 volts between pin 6 and 5.. And car won't start. I changed ecu engine and body computer and key.. But another wont start. Meccatronics my land won't work its because not experience. You are idea? Thank you

[@MechanicMindset]

Follow these basic steps for CAN bus diagnostics 👍 kzbin.info/www/bejne/oWnFe5idi92ilcU

[@johnbickle4654]

Hi , could could you give some advice if you have the time please

[@MechanicMindset]

Hi John, how can I help?

[@johnbickle4654]

@@MechanicMindset thanks , i have a 2010 renault scenic front wipers have stopped working done some basic checks each side has it's own motor getting 12v , ground and the 2 smaller wires have around 8 v , when i move wiper switch i'm getting a small change around 0.5 volts in these smaller wires , looking at live data in the uch when switching the wipers on it will change to on but only for 2 seconds and back to off again , The other thing i have noticed with the bonnet up and engine on there should be a warning light for bonnet open but nothing , i'm using a delphi ds sadly no live data for the bonnet switch any advice on direction would be greatly appreciated . also with both motors unplugged it's not setting any fault codes ?

[@MechanicMindset]

@@johnbickle4654 Ah ok, I must admit I’m not familiar with the set up. Unlikely to to two motors failed so I would be looking go for common factors for the two. The bonnet sensor could be a start; I know a few vehicles inhibit the wipers with the bonnet open.

[@johnbickle4654]

@@MechanicMindset Thanks , Do you think this is a lin bus control as it's showing around 8v on the two small wires , someone said the driver side is the master and if faulty both won't work , i thought the bsi (uch) would be the master and motors would be slaves keen to get this solved where can i learn how this type of system works had a look online but can't find anything? Thanks again

[@MechanicMindset]

@@johnbickle4654 Ah yes, likely. I do remember a similar system in Seat Leon when I was at VW. You got a scope to check it? He’s right, the master needs to be working so they don’t clash

[@MechanicMindset]

Mechanic Mindset Diagnostic Coach program is here! Click link: www.mechanicmindset.com/diagnostic-coach

[@jamesbarratt593]

Maybe. First gonna check resistance of can h and can l. If wires buggered that’ll be the reason.

[@smamas114]

What about DTC error code "D37D -can bus fault (intermittent) ".... the car has no simptome

[@x7royalhbb943]

i think can low speed must have reading on high :0.3v and low:4.7 when the reading on can high speed .high: 2.6 low:2.3

[@MechanicMindset]

That sounds about right 👍

[@SS-U23]

I am confused about shorting CAN wires. First you shorted CAN L wire to ground and CAN H to ground. Then you are shorting CAN H and CAN L to ground again, aren't you? Are you referring to CAN Low speed and CAN high speed? Then for each there is CAN high level and CAN low level? For instance, CAN high speed H level at rest is 2.4V and CAN high speed L level is 2.6. for the low speed CAN H level at rest is 0.0V and for CAN low speed L level is 5.0V. Is this what you are doing? I gotta watch it again. Thank you

[@MechanicMindset]

Can’t remember without watching the video. There may be a short together, and a short to live too. Voltages you mention there are about right for high and low speed 👍

[@pmo3448]

Does the car have to be completely asleep for these measurements?

[@Wrencher_86]

This is good stuff but not presented clearly. Some text on screen showing what fault you've introduced on what leg of the BUS and what the readings are on each leg of the BUS would be incredibly helpful. Would also turn this video into about the only source online that has those values clearly listed.

[@MechanicMindset]

Hi Zac, thanks for the feedback! I try to keep the videos as short as necessary and try to make it as simple as possible. We can appreciate that the diagnosis of CAN is a large subject! Would you be interested in a more formal online training course hat covers all aspects of CAN (and other networks) diagnostics?

[@Wrencher_86]

@@MechanicMindset Ha! That's a funny question because I was actually looking for resources to make it through an online assessment test for the manufacturer I work for when I found this video. I do a fair amount of CAN diagnosis at work. But A) CAN buses usually don't fail with direct shorts or opens and B) DVOM readings aren't how I approach diagnosing CAN faults. I use a scope or graphing meter to look at patterns and then isolate modules until the bus comes back online. The manufacturer I work for typically uses hub networks with central bus bars where you can disconnect modules one at a time until you isolate the problem branch. Short answer: No thank you, I have training provided to me through my work. But thanks for the polite response.

[@MechanicMindset]

@@Wrencher_86 👍 Do you work for Audi? PS I have a few other videos diagnosing with a scope, it sounds like you might like the one where I use a decade box to dial in fault resistance

[@seasonedtoker]

I'm gonna bite the bullet and post this million question dollar here - why do cars and modules go to sleep after a certain time? What is this open time representing? Can't a module be given a simple message to shut itself down after ignition off/locking, the same as it receives the wakeup msg? I have an E91 with TCU and yes you have guessed it I never ever figured out why the heck this thing keeps the car awake for almost an hour before it goes to sleep. I thought okay the E91 is a 15 yr old car and the luxury doesn't boot fast. But then I had an opportunity to see what G-series BMW does and it is practically the same. This is almost like turning off your phone completely, but it will still keep the cell and wifi connections on for 30 mins... What's the point except power exhaustion?

[@MechanicMindset]

Great question, and lots of reasons! ABS - allows ABS function to continue should T15 be lost while driving (same for SRS). COOL Down - some routines are executed after key off like EGR cleaning and cooling etc. CLIMATE Control - hold the valve in heating closed so you don’t get a blast of hot air after stopping at shops. PHONE - allows phone calls to continue after turning key off. BRAKES - electric handbrake re-applies after stopping due to brakes cooling. I’m sure there are many more reasons too, this just off the top of my head 👍

[@leeancroft7805]

Your videos are not clear enough