Multiple Modules Not Communicating, Where To Start?

Here we have a 2015 Chevrolet Malibu with a somewhat strange concern. The key is stuck in the ignition and it also will not crank. A Prescan using the Topdon Phoenix Smart show on the Topology there is no communication with several module. How do you approach complex looking communication faults?
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[@JoseSilveira-newhandleforYT]

Great approach to the problem, Jake! Turns out it was not a CAN branch gone wrong, but the BCM itself. Excellent job!

[@charliemagoo7943]

Such a relief to find a channel that doesn't claim its been to 5 dealerships that couldn't fix it. Heres a tip for rpo codes on gm vehicles: if there is a qr code on the door label scan it. Theres your qr codes. Rpo codes

[@john7017]

Jake, keep these troubleshooting video's coming. Easy to follow, right to the point. Thanks for sharing.

[@cccspokesmanandcofounder]

Love watching someone elses thought process in these situations.

[@paulspeller968]

absolutely spot on . don’t get overwhelmed with the amount of codes or module issues . look for a common thread pick one and run through your fundamentals. good service data is key 👍 excellent video mate showing keep calm and pick a spot then work one way or the other with the evidence you start to accumulate as you test

[@naushadali95]

you are a great diagnosis technician.

[@tomcarrigan902]

Other great diagnostic logical path, thank you again wizard.

[@prashanshan7125]

Good logical diagnostic work..!

[@cullenmiller8170]

Great video and diagnosis. I was thinking of a module under the seat being swamped during the detail process since it started having issues right after that.

[@spirokattan3655]

Jake, Great case study, tech tips and teaching skills. Thank you!!

[@josedejesusvelazquez6863]

Nothing equals the satisfaction of having made a great diagnosis, my friend. Greetings from Tijuana. 🇲🇽 Mexico 👍👍👍. 👋😜

[@raymondmetcalf9110]

JAKE Great video again.Keeping things simple powers and grounds and working from a different starting point to get to the same answer to prove it was the bcm good diagnostics.Cheers.

[@raviautoscanning]

Great diagnostics.

[@johnz8210]

Excellent as always. Thanks for doing these videos.

[@hpelisr]

Good job, That was very informant process.

[@don.timeless4993]

awesome job

[@darrellsdiagnostics9207]

nice diagnosis Jake very informative

[@PaulCTownsend]

Good job and I'm impressed.

[@mikechiodetti4482]

I like the way you test the wake up output, also quick check of the comm for integrity. You answered a question I've had, at least I think you you did. I have a 2020 Toyota RAV 4. When the driver's door is opened there's one "ding" from the "key in ignition" chime. Just one. Oh ya the interior lights also come on with the door opening. I'm thinking that wakes up the BCM and readies the other modules. The other noticeable sound is when I put the key in the ignition and before it's turned to on, the fuel pump in the gas tank is energized for two seconds. So that one event of opening the door and key inserted in the ign lock completes a lot! So thank you for this video, I'm glad you found a bad BCM and could replace it. Also thank you for helping me understand what my Toyota's doing.

[@samrugtiv3839]

Real good job jake.thanks for your good experience. Sam

[@neverstoplearning382]

Amazing diag and explanation. Thanks again.

[@manoramachandran9192]

Thank you for your time sir

[@richarddiaz8248]

Love the terminal test

[@user-te3pn4pb4u]

i always like the thought process these guys use. its not to solve an issue i have on any veh , its why they start where they start and their thinking. most guys like if i ask why when you remove a valve core from tire why does the air come out they look at you like dah they never relate to pressure differential or why the stem gets cold .you tell them the new ac condensers are filters now for the particles that start leaving a faulty compressor, they are dismayed. when i was first told that i dissected one to understand and yes it was true. when i watch these new techniques of testing i put it to the test for myself to prove or disapprove of their test. bottom line if you want to learn all this new stuff it takes dedication and a passion. cooking has things to do with what we do .like a pressure cooker relates to our cooling system. cooking with olive oil on stove and drop water in it if you understand that violet reaction that happens , not that it scared the crap out you but what caused it to take place, thats the thinking and understanding part ,knowing why it did it. pressure, volume and flow applies to electricity, fluids ,air etc, once you connect the dots you can trouble shoot many things not just automotive. keep them coming love it

[@Grunter123]

Too good Jake, and great tip about using a size small terminal for doing drag testing.

[@mrfreeze4245]

Thank you for sharing your wealth of knowledge

[@robertfrancisco1193]

👍👍👍nice work !!!

[@richarddiaz8248]

Perfect I will review them thank you for your knowledge and expertise

[@jtjones4727]

Wow you are the man. Another spot on diag. I always learn something watching these videos.

[@wime6478]

Great videos, good explaining Greetings from the Netherlands Wim

[@jgeorges3061]

Jake, AWESOME approach and thought process you rock brother thanks for sharing. cheeeeeeers

[@r.weaver3769]

So many times the first thought is a damage CAN line or bus. Awesome diagnosis. Thanks

[@nickayivor8432]

Tutorial brilliant Brilliant video 👍 ASTUTE Automotive Diagnostics & Programming From Nick Ayivor from London England UK 🇬🇧 ⏰️ 23:14pm

[@hddm3]

Man great video! Great tips. Thanks so much! Godbless

[@robertfoilesjr1337]

Jake! Excellent teacher. Please share your knowledge. I’d like to see how to check integrity of com system via data link step by step of time allows. Thanks

[@KASAD0]

Good job 👍👍👍

[@luismartinez1824]

Really enjoy watching your video's. Thanks for taking the time and being very informative as you processed with your diagnosis. It is very helpful and informative.

[@luismartinez1824]

Did you make those test bulbs with banana plugs yourself or did you purchase them ?

[@bobcombs7138]

Awesome diag Jake! Great strategy and thank you for taking the time to show how to track the problem down from a different module other than the BCM. Of coarse you knew the BCM was the power master module (sends the wake up voltage to other modules) but you went above and beyond to show that there is more than one way to get to the source of the problem. I've always been impressed with how you use both the meter and the test light to prove circuit integrity and voltage drop. I have one question about a BCM. If you have a sensor on the BCM, and the reference voltage to that sensor gets shorted to ground, can it cause no communication to the BCM? Or if a sensor is shorting the reference voltage to ground internally? I know in this case that wasn't the issue but could it be something that could cause issues? Thank you for another great video! Look forward to all your content!

[@autodiagyt]

In my experience no the power regulator to the mcu chip is separate from any sensors but I have proven before that a shorted sensor circuit to battery power could cause damage to the mcu. That’s just extremely uncommon scenario though.

[@sleathers1551]

great video.mental notes are made.i believe that sometimes we as techs get lost in all of the stuff in these cars,myself incliuded,it really all comes down to basics and to keep it as simple as possible.

[@arthurfricchione8119]

Jake thank you for sharing the fix and process you used for finding the fix. You are one heck of an instructor. I belong to two other testing classes one is Hands On Auto Training with Brian Mann and the other is Darren Quinn in Mechanic Mindset and all three of you are excellent . You stay on topic and and teach. You don’t just tell us the repair you teach us the process. Like you already know Im a DIYER I know the mechanics of cars but in todays world of total electronics well I’m trying like hell to get it together. Thanks again for sharing your knowledge. Artie. 👍

[@martinarrieta248]

Grasias

[@cgrs13]

Man thanks for the amazing content I have learned a lot from your videos. Keep the content coming in a huge fan! I’ve been able apply what I have learned from you here on KZbin Thank you 🙏

[@autodiagyt]

Awesome!

[@johnknox5692]

thk for video that is vantasic

[@aymenmohamed1134]

Awesome

[@Ahmed.Diesel]

Great ❤

[@MaartenP-vd3mo]

Another great case study Jake. 1 question; Aren't you afraid to disconnect the battery at the beginning of the diagnosis? I have had can bus failures that were - temporarily - resolved after a 12v reset of the battery. Well, in this case it won't be the case with a hard mistake, but I did wonder... Greetings

[@autodiagyt]

No once I have my prescan I'm not worried. If the concern clears then it was probably in a logic lockup(frozen) and the power cycle fixed it and I go about my day. If it Repeats then we need to test powers and grounds.

[@bbeauregard4181]

I hope Rock auto plugs are good!

[@alrifainidal]

Another great video! Thanks for your time. when you supply power does the car will start or just communicate?

[@autodiagyt]

Just communicate. The bcm handles immobilizer so the ecm never sees a ok signal to crank.

[@alrifainidal]

Thanks for ur reply

[@alrifainidal]

Thanks for ur reply

[@Saykes1994]

14:41 Hi Jake, how many bulbs do you have and which ones to check for power and ground?

[@autodiagyt]

4 or 5 and it depends on the circuit I’m testing which one I use.

[@chubbychequer1512]

Good evening what wattage bulb are you using to load test the circuit. Thanks

[@autodiagyt]

My go to bulb is a 3157. I can use it for a half amp load, 2 amp load, or stack both for 2.5 amps.

[@Bikerman42]

Good video. I was wondering how do you like the topdon. Is it as good or better than Autel?

[@autodiagyt]

They compliment each other. Almost always if one is missing something the other has it. The topdon is my daily right now and it's pretty good.

[@reggiemcnair1030]

Hey Jake thanks for the awesome content. Is it possible that you can do the one with GHE FORD EXPEDITION THINKS YOU LEFT THE KEY IN TBE IGNITION PLEASE SURE HAVE THAT PROBABLY

[@autodiagyt]

I've never seen that

[@reggiemcnair1030]

@autodiagyt thanks for replying back jake but I'm having that issue now my ford expedition thinks I left the keys into the ignition and I remove the key but my temp light oil light service engine light abs light and the chime noise stays on so i disconnect the negative terminal from the battery so it want make the battery go dead. Could you please help me out smh

[@autodiagyt]

@@reggiemcnair1030 if I had the vehicle I could diagnose it but there isn’t really anything I can do without research and testing.

[@reggiemcnair1030]

@autodiagyt Jake I took the terminal off all night drove great all day until tonight went in the store came back out and the service engine light was on the temp gauge then tried to start it an it wouldn't crank. Unplug the negative terminal to reprogram the computer and it started back up smh it's frustrating at this point

[@autodiagyt]

@@reggiemcnair1030 yeah I bet where are you located and I’ll see if I can recommend anyone in your area.

[@DuaneDonaldson]

Very much appreciated but you forgot a test at the end, you showed the nice TOPOLOGY at the beginning and made a guess as to what modules were not online but you did not show the fully working TOPOLOGY at the end after the fix please. 12 or 13 or 15 based on other Malibu I have seen but no firm record on a 2015.

[@autodiagyt]

Yeah I was in a hurry and just programmed it with sps and cleared the codes and everything worked and no codes in gds. Takes to long to rescan just to get a topology green screen. I really don’t care what modules are equipped because it can be different from one to the next. Swapping tools just to see that tree has no value to me when gds shows no codes after a key cycle and crank. The topology does come in handy at the start because it’s modules I know it’s equipped with, there was 2 more modules offline that I didn’t know was there until looking at the rpo codes and the wiring diagram but it’s still irrelevant if you follow the symptoms and have a good process in place.

[@mikemontenegro9426]

I'm like a sponge,,, love the crank no start ones❤

[@jordysandino6577]

Thank you mister jake for another great lesson . Quick question. If we don’t have power at ebcm can we bridge it ? Conect power from + battery? In pin 33 Will it comunicate then ?

[@autodiagyt]

Yes it would but would be better to test at both ends of the circuit to make sure you don't have a broken wire.

[@jordysandino6577]

Thank you sir. Many tech say that you can bridge the can lines and verify that ended that is the problem.

[@jordysandino6577]

Hello sir I’m watching this video again. How to know Wich letters to pick from the build sheet ?

[@jordysandino6577]

Thank you sir .

[@autodiagyt]

@@jordysandino6577 you compare your diagram rpo codes to your build sheet and look for the ones you have and don’t have

[@bigo975]

Is that a 1157 bulb u using for test light?

[@autodiagyt]

3157

[@thomasdemarco617]

you play chess most play checkers, can you please explain how you run a bulb thru your meter, connectors used etc I would appreciate it connectors and probes are often overlooked and are vital in this type of work plese help

[@KANDiagnostics]

What will be the terminal resistance value if it had all 3 120 resistors

[@autodiagyt]

It wouldn’t. The wiring harness would be completely different. But the math would be 40 ohms.

[@joeandgod1]

Was checking the communication wires coming in and out of BCM not necessary? I'm just trying to learn like everyone else.

[@autodiagyt]

No because the scan tool has to pass data through the BCM before it can communicate with anything else on the can bus. So this along with the ohm test at the dlc confirms good data wires in and out of the bcm.

[@richarddiaz8248]

Can you show us next time the programming of the BCM

[@autodiagyt]

I have a few videos showing the process of programming gm modules. I even have a dedicated video start to finish about programming new modules with gm. If you are wondering about doing a BCM specifically I have a video on a red Camaro that shows it.

[@ktcarroll4723]

So the ohms check at first confirmed wire integrity on can ? battery powers and grounds were good so ignition power was the culprit and that comes from bcm and as long as wire is not shorted it has to be a bad bcm?

[@russellhltn1396]

That seems to be the thinking, but I'd be asking what turns on the BCM. In this case, I'm guessing the key controls the ignition relay directly so "powers and grounds" covered that.

[@autodiagyt]

The bcm never fully goes to sleep it’s monitoring several things like a door opening to then fully wake it up and then it wakes up any other modules that might need to be used. So the bcm is basically responsible for waking itself up.

[@russellhltn1396]

@@autodiagyt Ok, but it still needs an input to do so, be it the key or the door switch.

[@autodiagyt]

@@russellhltn1396 yes even a scantool sending a message on the can bus will wake it up.

[@GregoryBirulkin]

Why did the ignition key failed to come out of the ignition lock?

[@autodiagyt]

Bcm has to release the key lock. If it doesn’t see park the key can’t rotate to off.

[@GregoryBirulkin]

@@autodiagyt thank you.

[@chulito240]

Don't know what year it started. Scan the QR code on the vin sticker in the door jam and bring it up as a notepad. That's you RPO sticker now and days.

[@abdul-kabiralegbe5660]

I dont quite understand. I would have thought the RPO codes on that BCM wiring diagram meant the BCM had that terminating resistor since the vehicle had those same RPO codes too. EDIT: The diagram says "-" meaning "minus". So any other RPO codes would've had that terminating resistor.

[@autodiagyt]

If you see the minus on a rpo code branch you ignore that branch.

[@rrmech11]

Right direction cause the key stuck

[@ktcarroll4723]

I would have closed the hood and shipped it down the road 😅