GM M.O.S.T. Bus Testing Made Simple!

[@JoseSilveira-newhandleforYT]

Great diagnostic, Jake! Of course, M.O.S.T. of it is pure knowledge 🙂

[@sollykhan2385]

Thank you for this excellent tutorial, you made it look so simple and straightforward with a no-nonsense approach, please post more, and you deserve at least 2 billion thumbs-up likes, and at least 500 Million subscribers 😇

[@firstlast---]

I like the test light idea better than relying on the min max function. Great video

[@ryan.mullen]

Super interesting. I sold parts for bmw for 15 years. In the parts department we stocked a “most bus loop” that we would have to hand out. I never knew what it was for. Now I do.

[@JessClearyAutoRepairLLC]

Cool video, I just went through this myself on a 13 lacrosse. Once you install the replacement, the radio will theft lock, you'll have to do a reprogram on the radio with sps2 to get it to unlock. If you try to do a replace, and reprogram on the media player listed on sps2 you'll get a no calibration error (that's for the other disk changer rpo). That cd player is automatically reprogrammed when you do the radio in sps2, they treat it as part of the radio. (Correction, it was a 2014 lacrosse, thanks for catching that Jake!)

[@autodiagyt]

Service Information says it should only need programmed if the vehicle has rear seat entertainment. Did you get a used one? Maybe it was configured for that?

[@JessClearyAutoRepairLLC]

I did get a used one, from a salvage yard, so I'm not sure if the car it came out of had rear entertainment or not. But when I plugged it in, the radio went straight to theft lock.

[@sleathers1551]

Good tip

[@autodiagyt]

@@JessClearyAutoRepairLLC I just looked and a 2013 lacrosse doesn’t use a most system so the cd player you replaced is actually the radio, so yes it needed programming.

[@JessClearyAutoRepairLLC]

@@autodiagyt sorry, it had a build date of 2013, but was a 2014. It had a MOST set up though for sure.

[@SouthMainAuto]

Ever ran across these when the most master (radio) is the module that's down?

[@autodiagyt]

Yes! If you bypass every module in the loop one at a time and never regain either a screen display or audio and you have no breaks in the lines it's a probably a bad radio or you got very unlucky and it's a bad amp and HMI lol

[@SouthMainAuto]

Seems like every time I have delt with a MOST bus issue it has always been a bad radio making it a bit of a pisser to diag. I saved a real well written document on MOST Data Bus diagnosing that was very helpful and I refer to it anytime I run a across one which isn't to often thankfully.@@autodiagyt

[@truth4reel]

2013 SRX. I had a bad HMI and Radio. Bad grounds and pin drag issue on white/green MOST bus line wire going into the HMI. That was a head scratcher. I had to disconnect the battery to get the number of MOST breaks to reset every time I swapped a module or jumped something.

[@thesmartguy3523]

Had a similar case on a Toyota LC200 a week ago, had a break in the MOST bus between the AMP and radio

[@mikechiodetti4482]

Thank you for this quick check tip.

[@ratrodnation]

Great troubleshooting information 👊

[@fredautos]

Quick awesome Tip

[@jaustin3370]

Awesome! Thanks for sharing your technical skills!

[@globalcommerce7654]

Good video, I did a video on this for a Silverado about a month ago I believe.. Guess what? Ended up being the CD player as well! Seem like the CD player might be a common fault to bring down the bus on GM, first thing to pull guys if you run into this as a shortcut..

[@autodiagyt]

I find it’s usually the HMI lol. I have a video on a bad HMI.

[@lupedelacruz4152]

Great work Jake thanks for sharing amigo

[@saiautorepairs]

Awesome video thank you for sharing

[@agoodneighborautorepair2176]

Very Good information and explanation

[@mrwayne70]

Great video Jake. I always thought MOST ran off light. It was on the BMW’s I used to work on. May be different in the States

[@autodiagyt]

Yes MOST can be Fiberoptic or Wire. They both are similar that they are Ring networks and each module in the loop reads the incoming data and then outputs it down the line. It if a module doesn't communicate it ends the loop and nothing works generally. If a line is broken same thing, nothing works.

[@advancedleveldiagnostics]

Great diag, Thanks for sharing! Last time you had a video on the most bus you used a special tool from GM, which I had my eye on for a while lol

[@autodiagyt]

Yeah I don't own that tool sadly. It makes it easy and fast but this way works the same. I think that tool was close to $500 if I remember correctly.

[@sollykhan2385]

@@autodiagyt Home made substitute tools and accessories can save a lot of serious $$$$'s , 500 Bucks is a crime, esp fro struggling Mechanics, where we never stop spending money on tools, as Snap on guy's live a comfortable life on our hard work!!

[@roberttwiford2010]

If your ever looking for gm terminals of any kind done hesitate to reach out! I bought the six tray terminal repair kit kent moore supplies the dealers with and have more than ill ever need. It might be a day or two before i gets to you being im in indiana. Mainly been using them to build my own scope/breakout leads and quick repairs. But needless to say with six trays with each tray having 30+ types/styles. I have no problem sending you something if you need it!

[@eljuliel]

I would like to test my MOST BUs connections with connectors and add jumper wires. Would this be something you can help with??

[@arthurfricchione8119]

Jake another good informative video. Thanks for sharing. 👍Artie

[@stevemazzarella7212]

Nice!!!

[@djosbun]

You can get the Micro 64 male (and female) from Mouser Electronics.

[@autodiagyt]

Awesome thanks!

[@GeneG-wk2mz]

Nice work this must be the launch new scanner

[@autodiagyt]

Yes it is. I go between it and the topdon phoenix smart every day. Just depends on which one needs the battery charged back up on lol.

[@GeneG-wk2mz]

@@autodiagyt which model is this one ?

[@autodiagyt]

@@GeneG-wk2mz launch pro3s+ it’s linked in the amazon store

[@SeanHill-t3u]

where do you get your banana jack connectors that are on your 2 amp bulb

[@autodiagyt]

In the video description there is a Amazon link where you can find them

[@mikeburchett-bs3qw]

good info 👍keep them coming

[@NoName-yr1jv]

Well done 👍

[@robertmobileman8304]

awesome Jake nice one

[@8power0]

THANKS FOR SHARING ,,,,,,,,,!!!!!!!!!!!!!!!!!

[@NPCmechanic]

Thank you!

[@secretsquirrel9722]

Gives me ptsd from bmw MOST diag's which were fibre optic. A single fault (usually bluetooth module toast) and a dozen units down. Plus, a HUGE bill if out of warranty. Or a loop out of whatever control unit, haha.

[@cullenmiller8170]

Great video and explanation. If you didn’t want to replace the media player could you just cut the four wires and solder them together to bypass it?

[@autodiagyt]

Yes

[@JACKATTACKED]

👍

[@jgeorges3061]

AWESOME approach and thought process which scanner u using is it LAUNCH as always thanks for sharing.

[@autodiagyt]

Yes this one is the Launch Pro3s+ there is a link to it on my Amazon store. Great tool that I've been using daily along side my topdon Phoenix Smart.

[@mikecrilly5478]

Very good! I'm dealing with a 2018 Caddy CT6 intermittent no audio & video touch screen when it does not work have a fixed 12 Volt on the Network serial 5 when it works i see comm. message on that circuit have trouble finding any info on that network. It just goes between HMI and the Video touch screen any suggestion would be great

[@autodiagyt]

Find my other video on a Tahoe with a bad HMI unit. It would have been back in 2022 I believe.

[@Santiago_Ordonez_]

Nice. 👌

[@paulspeller968]

oh yes the joys of most bus or the old d2b bus mega fragile silly light transfer bus on old mercedes used to have a rake of those old jumpers in my box back in the day to bridge out units one by one . back then the diagnostic capability of scan or even dealer tools was pretty limited. so a lot of the time it was poke and hope 🤣🤣🤣🤣

[@autodiagyt]

Yep this wired system operates very similar to the Fiberoptic most bus that European vehicles use.

[@eljuliel]

I have black-lit screen on my 2019 yukon. But no radio. Cluster says audio Off. Revese camera works but screen is black and radio does not work? Could it be the HMI module???

[@autodiagyt]

It can be anything on the MOST bus. But generally yes if it’s a black screen it’s the HMI.

[@viplegaleducation1292]

Just curious why you used the launch here over the topdon?

[@autodiagyt]

I go between both of them daily. I just grab which ever one isn’t charging. Software they are pretty much the same. The Topdon phoenix smart does more stuff but the day to day stuff is about the same. The launch is much faster at connecting to a vehicle though.

[@JOHNPHUFNAGEL]

I love MOST of your videos.. Lol

[@joeandgod1]

How do you like that scan tool?

[@autodiagyt]

I like it alot actually. I use it daily along with my Phoenix Smart. Pretty much just go between those two. I grab which ever one doesn't need charged lol

[@joeandgod1]

@@autodiagyt Ok. That will probably be my next one, thanks.

[@Max-j2r]

❤❤❤❤❤❤