Quick CAN BUS Check (aka Fun With Resistors) - Wrenchin' Up
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- Опубликовано: 7 сен 2024
- Tracking down the source of U codes can be challenging, but this quick check of the condition of the CAN Bus can be a helpful part of your diagnostics. It may even help you discover the problem right away. Be sure to check the service or repair manual for the vehicle you are working on to be sure of the resistor values on the CAN BUS as it may differ from the example in this video.
The video also has "Fun With Resistors" in the title (I couldn't "resist" that) because it may be helpful in understanding how resistors behave in both series and parallel circuits.
Wrenchin' Up with Jim Bates strives to deliver automotive technical information and ideas from manufacturers and engineers to interested technicians and enthusiasts on a weekly basis. A new video is uploaded almost every Wednesday.
Due to factors beyond the control of Wrenchin' Up with Jim Bates, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. Wrenchin' Up with Jim Bates assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. Wrenchin' Up with Jim Bates 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 Wrenchin' Up with Jim Bates, 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 Wrenchin' Up with Jim Bates.
Twitter: @jimfbates
![How To Test CAN BUS With A Multimeter [CAN Bus Resistance Check] Mechanic Mindset](http://i.ytimg.com/vi/JPE42HSJxAk/mqdefault.jpg)
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As an electronics hobbyist, I think you explained the resistor basics extremely well for those who are a bit daunted by this stuff.
A good quick refresher in electronics fundamentals to better understand the CAN circuit. I bought a Power Probe breakout box to make my life a little easier
Hi - Thanks for watching and sharing your experience!
Thanks, I wondered exactly what made the CAN bus 60 ohms....now it will be easier to remember :)
Hi - You're welcome and thanks for watching!
helped me a lot to understand can bus,I don't care what the hater commentators say.
Thanks for the comment and Thanks for watching!
Very well done video. Making it simple is the key to understanding "complex" diagnostic problems.
Hi Brian - Thanks for watching and for your comment!
This video did help me with an understanding of can bus. What this video really helped me get a solid grasp on is, the pairing and wiring of speakers and amplifiers. Thank you. Maybe I'd lacked to pay attention in countless amount of car audio videos. Either way, much needed information clicked for me here. Thanks again 🤙
Hi - You're welcome and thanks for watching!
Thank you, the information applies to big rigs and transit buses
Hi - You're welcome! Thanks for watching and sharing your information.
👌thank you sir, you just explained something - in a flash - i couldnt get at college level in a school for electricians 😍👍👍👍👍👍
Hi - You're welcome and thanks for watching! I'm glad the video helped.
Also thank you, once you started to compare series to parallel I understood immediately the difference in ohms at different spots.
Good job Sir,....All salute goes to you !!!! !!!!
Hi - Thanks for watching. I’m glad you like the video!
Thanks Jim Bates, Cars that use TIPM totally intergrated power module our in Chrysler cars. The TIPM uses CAN Diagnostic signals and CPU chips to control modules and sensors. If you can find out more how these TIPM work and are used would be a big help.
The TIPMS is the "gateway" module . Chrysler however does not allow direct access to its CAN network via the DLC. It is instead a diagnostic only circuit and Pin 6 and Pin 14 are held high at 2.5V always looking for something that's is plugged in and drops the voltage. It will these begin to transmit or try .. You must lift the TIPMs up from its holder and flip it on its side to gain access to any 1 of the 3 networks and must use a diagram to know which twisted pairs are for what network .
The methods in this video will not work on a Chrysler that uses the TIPMs gateway module . He also forgot to explain time outs for the network before you attempt to measure. An network that is awake and talking will display millions of ohms and will be bouncing all around . He didn't mention that you must wait attest 5 minutes for the modules power down and that some vehicles wake back up to run EVAP testing . Great video but left out some details
Great speaker and teacher!
Hi - Thanks for watching and for the very kind comment!
Oh boy did this help out alot! Thanks! Tring to figure out a Can C on a Dodge Nitro . I was thinking it was a wiring issue. Now I know its not! Got a bad module some where.
Hi - Thanks for watching and sharing your experience!
Thanks for helping me of this information 🙏
Hi - I’m glad the video helped. Thanks for watching!
thanks alot sir.your video was short but very useful because you explained it in a simple way,i was looking for an instruction like yours about a month in google but i had found alot of long video which explained alot and repetitive and similar that didn't help me. i 'll follow your channel and suggest it to all of my partner.👍👍👍👍
Hi - Thanks for the very nice comment and Thanks for watching!
Helpful video thank you v
From Nick Ayivor from London England UK 🇬🇧
Hi Nick - You’re welcome and thanks for watching!
I have the same Multimeter as you. it was given to me by a customer who found it in the house they just moved in to
Hi - Thanks for watching! I have several good DMMs and used this one in my live workshops quite often. It’s held up well.
Iam so. Behind 😩 great video
Hi - Thanks for watching!
Hi Jim, the Resistors are divided, when connected in parallel, because they are equal and equivalent Resitors value is 60 ohm. It's a particular case. For example, one would be a 140 and another of 100(their sum is the same 240) but the equivalent Resitors value is 58.33 ohm.
Hi Ovidiu - Thanks for your comment. Let's see how others digest this. Thanks for watching!
Difference of 1.7 ohm , not a big deal. Thank you for your very concise explanations about CAN Bus. Thumbs up!
Very good explanation
Hi - Thanks for watching! I'm glad the video is helpful.
Excellent explanation
Hi - Thanks for watching and for your nice comment. I'm glad the video helped.
After the intro I thought I'd finally get an answer to my problem but by the end all my hair had turned gray 🙃
Hi - Thanks for watching and sharing your experience!
Good job Sir
Hi - Thanks for watching! I'm glad you like it.
@@WrenchinUpwithJimBates Thank you sir
Wow very good 👍👍👍👍👍
Hi - Thanks for watching!
great explanation, could you go a little deeper in the diagnostics process with a problem car?
Hi Christian - Thanks for watching! If I get the opportunity I certainly will, but in the meantime I suggest that you check out some of my recommended RUclips channels as they may already have whet you are looking for.
Very helpful tip
Hi - Thanks for watching! I’m glad you found the information helpful.
So simple a toddler can understand.
Hi - Thanks for watching and for your nice comment!
So easy a caveman can do it
Like! thank you very much
Hi - Thanks for watching! I’m glad you like it.
Thanks JIM BATES, make more videos please showing step by step when you get a BAD CAN bus signal how to find the bad CAN module that is cause it. Do you disconnect each fuse in the cars fuse box or physically disconnect each CAN module one by one until you find the BAD CAN bus? most CAN modules are hard to get it without tearing the whole car apart, there must be an easier way.
Hi Bill - Start by using your bi-directional scan tool to access each module where codes are generated. Then see if you can view sensor input and control the actuators. The inability to do those things indicate either a bad Buss connection, bad module or bad sensors/actuators. Use isolation diagnostics to pinpoint the problem(s).
Hey Bill - Just wanted to let you know that I have put this topic on my list. I'll interview someone who can answer the CAN Buss diagnostic questions you asked about as soon as I can.
JIM BATES, can you show how to use the SCAN tool to check verify each module, sensor, actuator and show what a GOOD CAN bus signal looks like and what a BAD CAN bus signal looks like?
Hi Bill - Thanks for watching! I'll put that on the list of videos to make.
E55 2003 amg Can bus shows 60ohms but there no communication with inside of the scan tool. I can see codes and what not but once I try and diagnose a module it says no communication. Here are the symptoms I’m having. Seats don’t work only lumbar and car doesn’t show what gear I’m in or manual sport mode on the instrument cluster. P0600 P203e-4 🤷🏻♂️
Hi - Thanks for watching! If the Can Bus is intact you might want to check the module's power and ground. Then use a bi-directional scan tool to read sensors and operate actuators for the suspect module. If no response, check the individual sensors and actuators associated with the module to see if the problem is the module or the sensors and actuators. If your scan tool is not bidirectional you may have to refer to the trouble shooting tree in a service/repair manual for the codes & symptoms.
It is great video👍
But Opel Vectra 1999model doesn't have 14th pin which is CAN low. That's why I can't check CAN bus data with my scope through OBD2 place.
As information I should say that, there is not any problem with diagnosing that Opel Vectra with computer.
Hi - Thanks for watching and sharing your valuable information!
I have 2013 volvo xc60 .I intermittent mamu lights coming.when lights come I lose cluster rpm and speed.windoews signals and radio.
Hi - Thanks for watching! Long distance diagnostics are difficult at best. What were the results of any diagnostics you have already done and what, if any, corrective procedures have you done?
You couldn't have said it simpler!
EXPLAINED WELL, BUT WHAT ABOUT WHEN YOU HAVE A GATEWAY MODULE IN THE CIRCUIT? I BET ITS NOT THE SAME, ESPECIALLY ON THE 2019 AND UP
Hi - Thanks for watching! This video was made years ago with the CAN Bus available at the time. The Buss was also used in explaining how resistors work in series and parallel circuits. Now, on later model vehicles, we have to check the wiring diagrams to see what's in the circuits we are testing.
Well, I see that the last entry on this podcast was 4 years ago. Jim, hooked up the multimeter and pin 4 and 14 reads 12.58 volts. Pin 5 and 14 also read 12.58 volts.
Changed the multimeter to ohms and pin 5 and 14 reads "0". Pin 4 and 14 also read " 0". Checked several times, same results.
What's next after that? Where do you go?
Hi - Thanks for watching! It depends on why you are doing this. If you have a "U" code pointing to a communications error and you have these results, the next step is to look at the other codes to determine which module(s) are associated with the sensor(s) or actuator(s) defined in those codes. Then using a bi-directional scan tool, attempt to communicate with the Module(s), read sensor inputs, cycle actuators, etc. to determine where the problem(s) exist.
Hello Jim,
I'm struggling with exactly this and I'm losing my mind.
'08 Suburban, 1500 4wd.
The entire "left" side of the canbus (high) is failing to communicate - Fuel Pump Control Module, Transfer Case, ABS.
4WD works (2 high, auto, 4 high - NO 4 low functionality).
ABS, traction control, and stabilitrac all fail to function.
120-122 ohms measured at pins 6/14 of the DLC, this remains constant even when the Terminating resistor is unplugged, each of the 3 modules is unplugged, and the C3 connector in the up-fitter box ("left side" of the high speed can bus) is disconnected.
I've used a Bluetooth Obd scanner, an up to date (2021 model) Snap-On bi-directional scanner, and two separate GM Tech 2 scanners to confirm that the ABS, Fuel Pump, and x-fer case control modules all consistently fail the handshake.
The truck runs and drives, even with all of the above disconnected. Going on 5,000 miles with the issue...
I have pulled and replaced every J case and mini blade fuse (US made, name brand fuses). I replaced the ground strap on the driver's side, the battery ground to the block, and both hot wires from the battery to the starter and to the fused distribution block.
I'm at my wit's end... I've even cleaned every ground and connection in the bay, within the cab, beneath the body, etc. with compressed air, slathered it with quality dielectric grease, and reseated it properly by hand.
None of the fuses/relays were blown, bypassing each module fails to help, and I'm just flat out of ideas. Best I can sort out, the can bus just died on the entire left high speed channel...
@@ChaoticWrath Did you ever figure this out? I have a 2014 Express with a similar issue.
Jim bates Thanks , what are the SAE J1850 signals and ISO9141 signals used for, do you use them for troubleshooting what? What are these different baud rates used for 500K, 250K, 125K? Every car has a central gateway circuit board that all the modules connect to a gateway circuit board. The gateway circuit board converts the CAN signals into SAE J1850 signals, ISO9141 signals, ILS signals? or what does this gateway circuit board do?
Hi Bill - The questions you are asking now are beyond me now as I haven’t been a tech for many years. I’m just a journalist and film maker now. I think the platforms of Scanner Danner, TST, etc. should be able to help you with your CAN questions. Thanks for watching though!
problem facing in Chevrolet captiva 2007 manual, DTC U0073(Control Module Communication Bus OFF), U0121(ABS MODULE lost communication) and P0500(Vehicle Speed Sensor) ,,,,suddenly instrument cluster stops working ,all needles(Temperature, rpm, speed etc.) showing 0 reading , ac stops cooling while blower keep running,reverse gear light stops working, Service Vehicle Soon light & MIL illuminates in cluster. and all happen intermittently and all together. Can anybody suggest solution?
Ash Kumar yo you ever find your issue
@@kencolt8850 yes, I bought complete module set from scrap/junk market and replaced.working fine till now 30days
Hello, Sir. If one of the terminating resistors is open, will you have 0v on CAN HI and CAN LOW at the dlc connector? If no, why not?
Hi - Thanks for watching! I don't really like commenting this way, but I suppose it will depend on the vehicle and complexity of the CAN system. If a terminating resistor is open the CAN circuit is open (CAN high) but the since modules are connected in parallel it might depend on where the test point is (I think). So without a wiring diagram for the vehicle and not being active in the diagnostic and repair business for quite a few years, I really don't know for sure.
My can bus was run through my radio that fried. O put on a new radio but had no hookups for it where should i run those blue cables on a 2010 chevy aveo?
Hi - Thanks for watching! The best advice I can give you here is to get the wiring diagram in a service/repair manual and see how you can bypass the radio. Not sure if some kind of relearn will be necessary if the system will be looking for a radio.
Tq sir
Hi - Thanks for watching!
Hello.
I have a problem with a can bus.
No u codes.
I can communicate with all the modules but i can't get live data.
As soon as I try read the live data on any module, the scanner takes me out and display a message of no communication.
I have literally done everything.
I don't really know what else I can do to diagnose the can bus system.
Hi - Thanks for watching! Looks like you're doing everything right. Does your scanner have up to date software needed to communicate with the year/model vehicle? If so, I would suggest that you contact the scanner manufacturer's help line.
@@WrenchinUpwithJimBates
The scanner is ok.
I can work on any other car without a problem.
This vehicle had a bad pcm that I already replaced.
I can read all the modules and I can read the trouble codes, for example but when I try to go in the live data, bidirectional data, it's like some mudule tries to communicate and makes a "noise" on the wavaband that stop the communication between the scanner and the vehicle.
For sure there's another module bad, besides the the pcm module that I already replaced but I don't have any U codes.
Hi - Perhaps if you try to command each module on the Bus to control an actuator you could isolate the problem one that is unable to do so.
@@WrenchinUpwithJimBates
Thanks for answering again !
This high speed system is connected in series in this vehicle.
I downloaded the diagram from GM.
It start with the pcm, bcm, ebcm to the tcm.
Let's say I disconnect the ebcm, I will not be able to read tcm.
I jumped the wires on the ebcm connector but I wasn't able to read the tcm.
I jumped the wires on the bcm and I wasn't able communicate downward the system either.
Pcm and tcm has the 120 ohms resistor.
Resistance on pin 6 and 14 of the dlc connector is 60 ohms.
I can read the voltage can bus low at 2.4 volts and can bus high at 2.6 volts.
I can communicate with all modules but I can only read the live data from the pcm and bcm.
Let's say that I'm in the bcm, live data, brake.
I can read the parking brake is released.
If I press the parking brake pedal, after 10 seconds the scanner will tell me that can't communicate with the bcm, same module I was able to communicate before.
It seems like there is some kind of "noise" in the waveband of the can bus when the system tries to communicate with the scanner.
I don't really know what's going on.
How would you approach a diagnosis like this one ?
Hi - Well, I've been out of the diagnostic game for about 7 years now and am certainly not "caught up", but I suppose I would mess around with an Oscope on the bus to see what it looks like and to try to isolate any noise I see. I would also call a diagnostic line if I was into diagnostics for more that 45 minutes with no conclusions in a shop situation.
Hi Sir i acedently put 12 Colts on the canbus hi /low all my ecu and modules in that circuit (9total crasht already put new in it and are coded) .. the obd2 still saying no communication ! The signal is not so good on the silloscoop i cut the canbus and solder it back together does that influence the signal if it's not done perfectly? And how do i do it so it's perfect again Please help me if you have any tips fore me thanks !
Hi - Thanks for watching! I don't haver that information so I'm not exactly sure. I recommend that you check a service/repair manual for the proper diagnostic and repair procedures, which is pretty much what I do in cases like this.
Respect
Hi K D - Thanks for watching!
Jim do you have any information/videos on the old G.M. obd I.5 , that's gm's transition year from obdI to obd II
Thanks
Hi - Thanks for watching! Sorry but I don't. Have you checked any service/repair manuals for a specific vehicle in question? That might help.
@@WrenchinUpwithJimBates yes I've have all g.m. service manuals for my cars with the 1.5.....alot of the trouble shooting is done with the old tech 1...ancient technology....I'm surviving with an Actron cp9145 and old time basics, multimeter and test light
Can you make a video about diagnosing a bad ecm?
Hi - Thanks for watching! I've added it to my list of future video projects.
any reasons why the CAN buss is 120ohms, how did they come up with 120ohms, where does it come from? It doesn't make sense to me why the CAN standard is 120 ohms.
Hi Bill - I'm not an engineer so I don't know how they came up with 120 ohms. Hopefully someone who knows will jump in here to help.
They use the two 120 ohm resistors (one at each end) to prevent the signal from bouncing back and forth (or echoing) in the bus. I guess they found that 120 is the value that worked best.
Hi, will you measure 60 ohms at pins 6 and 14 of OBD2 with the battery connected or disconnected?
Hi - Thanks for watching! The 12 volt battery was connected and the ignition switch was off.
@@WrenchinUpwithJimBates thank you sir. Great video and info. I have some more trouble shooting to do on my car. Car was in an accident but was running, bodyshop did some work and now car cranks but won't start and scanner will not link to ECU. I feel like I lost ECU ground or something. I read about 180K ohms at pins 6 and 14 of OBD2. I have 12 volts at pin 16.
Hi Arnold - I think you're on the right track. You'll need a wiring diagram to to check for the proper power and ground.
Hope you can help me out. Hooked up to pin 6 and 14 and got no reading at all. Tried it the battery connected and disconnected and made no difference. Any idea on why.
Hi - Thanks for watching! It's been quite a while since that video was created so here are some things to consider. Depending on the year/model of your vehicle there may be some changes or additions to the circuitry from the vehicle used in the video. You will have to check out the wiring diagram found in a service/repair manual to verify that, and if your "Check Engine" light is on there may be an open in that circuit.
Mr. Jim Bates is Fantastic , however ;
the Real Deal as far as CAN Bus Testing is from a College Automotive Instructor.
Goggle on RUclips Mr. Diagnosis Tech :
Watch the two videos labeled , Testing the CAN Circuit using a Voltage Meter and Testing the CAN Circuit using a Scope.
Thanks sir ,very good video.
By the way do you know where those resistors are physically located ?
Hi Daniel - I suppose it would be vehicle specific, but I really don't know. Hopefully someone with that type of knowledge (Hobbs?) will jump in here and comment. Thanks for watching!
Normally in ECU and in IC , but as jim say depends on vehicle and its models...!!!
Hi,
My can bus is 60OHM
But my radio come oof and on and flash lighting radio
What do you think
When I try to key on position the 60 ohm is gone !!!
Hi - Thanks for watching. Looks line the buss is intact. With key on there is voltage on the buss so you can't read resistance. I suggest that you use a bidirectional scan tool to communicate with the BCM or whichever module controls the radio to see if that's where the problem is.
@@WrenchinUpwithJimBates Hi.
Thanks for the answer
When I try to used the brakes or use some flash sign left or right going and on off
Do you think maybe for ground cable
Hi - Long distance diagnostics is difficult if not impossible but you may be on the right track. I suggest that you check a wiring diagram in a service/repair manual (available at auto parts stores) and check or replace problem wires and connections for those circuits. I had a similar situation with an older Jeep I traded for some years ago. Bad wiring was the cause and I replaced all of them using this method. It took the better part of a week but then I drove the Jeep for about 150,000 miles after that.
@@WrenchinUpwithJimBates
Thanks 🙏
oh wow! thank you for that,. it so helpful for me cuz im a beginner of scanner,. by the way i was scanned range rover last monday then the code is "CAN bus fault" do you know what the problem like this? thank you in advance,.
Hi - It's most likely a communications problem, either between controllers or between a controller and an actuator. Use your isolation diagnostic skills to pinpoint the problem. Thanks for watching!
Thank you sir,.
Exelente.
Hi David - Thanks for watching and for your very nice comment!
WHAT ABOUT CHRYSLER NO PIN #6 NO PIN# 14 CONNECTION. ONLY ONE CAN LINE?😕
Hi - Thanks for watching! This video was created several years ago to demonstrate how resistors work in series and parallel circuits using a simple (for the time) CAN bus diagnosis. I would like to suggest that you check a service/repair manual for information on the CAN System for the vehicle you are working on.
thank yuo
Hi - You are welcome and Thanks for watching!
If can buss is intact is the ecu/ ECM good???
Hi John - Thanks for watching! I suppose that if the ECM can respond to sensors and control actuators and play nice in the Buss it is OK. You could use a bidirectional scan tool to check those things out.
This 60 Ohms a same iso 9141 protocol?
Hi Jeffrey - Probably not. The video was published 4 years ago as a means to do a quick check of the integrity of this buss, and to provide a practical demonstration of what happens to resistance in series and parallel circuits.
My bmw said no comunication with the medium can bus , thats a problem ????
Hi - Yes it looks like a problem to me so be sure to check with a service/repair manual for your car for diagno9stic and repair procedures. Thanks for watching!
@@WrenchinUpwithJimBates but why it give me this codes if no comunication U0110 , U0111 in generic scanner ,can you tell me please
Hi - The codes are stored in the PCM and indicate that there are communication problems with other processors on the CAN Buss.
@@WrenchinUpwithJimBates ok but is not the ECU ???
I get 61.5 ohms at pins 6/14 is this acceptable
Hi Dave - Thanks for watching! According to the information I had at the time the video was created, 61.5 ohms on the CAN BUSS would be acceptable.
What the meaning of can bus
Hi - Thanks for watching. CAN (Controller Area Network) Bus is the wiring harness that connects the vehicle’s Engine Control, Chassis Control and Body Control computers together. Since these computers share some of the vehicle sensor data, they communicate with each other over this network.
What if my can bus connection read less.
Hi - Some vehicles these days may use different types of Buss configurations than the one in the video that was done some years ago. When the reading is not what you expect, be sure to check a service or repair manual for the vehicle you are working on to see what it should be. If the spec is the same as the vehicle used in the video and you are getting a lower reading suspect a short circuit somewhere on the Buss.
It was only about three minutes I thought you had 15 minutes worth of diagnostics for us to do. I just must have misunderstood.
Sorry to disappoint. But hey, I hope you found something fun or interesting or constructive to do with the left over 12 minutes. Thanks for watching!
can I ask you something
Sure
@@WrenchinUpwithJimBates I am trying to use a car radio from an old Fiat punto as a home Radio with a 12v power supply and when I try to open it, it says in the screen cancheck and it doesn't work, can you help me?
@@WrenchinUpwithJimBates Also I didn't connect 3 wires in the back. The AUT/ANT, can a and can b, because I don't know how
Hi - I really don’t have anything here that can solve the problem, but I suspect the unit sees an open circuit in the CAN Buss(s). I think if you refer to the wiring diagram for the vehicle's radio connections you might be able to figure it out. Check a service/repair manual (you might find one at the public library you could look at for free).
@@WrenchinUpwithJimBates OK thank you so much
In real life most problems are intermittent, this doesn't help much in those cases
Hi - Thanks for the comment. I agree that intermittant problems are tough to track down and since the procedure in this video is meant to find an open or high resistance on the early CAN Buss it won't be of much help in those instances. The other main reason for the video is to provice an example to look at how difference in series and parallel circuits can change the resistance in the circuits and the ohmeter readings. Thanks for watching!
I disagree these fundamentals point to whats going on intermittently. It's intermittently going to zero volts on which line? The the low one or the high. You still use the fundamentals to decide which line line and side of the circuit to look and also know what it it and isnt supposed to look like
Your resistance is futile.
Hi - Thanks for watching and sharing your comment. (Although the Borg should know better by now).