Gmlan no comm
Vehicle towed in with no crank no comms with any module on the gmlan bus, cluster always on with battery light and odometer. hooked up my ATS scope and saw that there was a short 7 volts on the bus. GM added a shorting box of all the modules bus lines to test them individually. Every module on the bus had a nice clean waveform except for the battery module and the PCM, discontinued the battery module and regained comms with every module except PCM and that was due to a ground voltage drop at its main ground behind the engine head passenger side. Grounded that blk/whire wire and vehicle started up. Any questions please let me know ! I’ve attached a known good gmlan waveform i found on google since my pc/scope died while making the video.
My biggest regret is getting the Zeus and not knowing about the Escope… Good job that was cool
I would absolutely recommend the escope or my personal favorite is my pico 4425a thanks !
Due to financial constraints, I bought an 8 channel Pico. Although Bernie is great and he has engineered some really cool features in the software, My purchase was 2500.00 cheaper. I, too, would have loved to have been able to afford the AST Escope! Peace!
Don't despair Sherman, Look at the advantages you have with the PICO. PICO has a waveform library (available to only PICO owners) that cannot be beat. It is not the tools using the tech, it is the tech using the tools that counts.
I did the exact same thing you did. I wish I could somehow trade mine for an escope
Thanx for sharing, so in reference to data lines you was talking about class 2 data 0-7 volts, was the bus lines break out at splice pack 205 ?
I believe so 205 pack under knee cover area right hand side of i/p fuse box.
Hi Aaron, Did you reconnect the battery module, then retest to prove it was only the broken ground or was the battery module also bad? You were a little scattered with the video, but good case study.
Yes actually i did reconnect the batt module to make sure and once again brought down the bus and the bad pcm ground itself did not bring down the bus only the battery module, yes my video was definitely kinda wack haha, thanks for commenting!
Hi Aaron. I appreciate your efforts, so don't take take my comments as being too critical. Editing and planning takes 5 times longer or more than what the finish product turns out. Many people take that for granted and do not realize the ‘real time’ effort. I am sure things will smooth out with more practice. Keep at it. Lord knows there are many people out there who need these kinds of ‘real…
Absolutely 1000% agree with you man, thanks again for the kind words ! if you dont mind me asking do you go to any online training ? i have avi on demand but always looking for more training
thanks Aaron for sharing it , very nice , I used to have AVI 5 years ago and for sure it really helped me a lot , also you can use CTI online training , they have live classes almost everyday , a lot of training there , TST training also , scanner danner premium, just to mention a few but a lot out there very valuable.
App the info felix will definitely look into it, I used to have danners premium, will probably get it again.
Hi Aaron, I use all the resources I can find for training, learning and information. In diagnostics, it takes an open mind and a willingness to learn and accept new ideas. Some people will criticize online resources like You Tube, but there are a lot of good offerings out there. Along with that, I keep track of vendors putting on mini classes and attend them when I can. Another resource is…
I recently found a high resistance ground causing a plethora of problems on a 2016 CX5 Mazda. But for the scope and a good DVOM, and a Dad who was a computer engineer for IBM…. well, 'nuff said! Woops! It was a 2014 Kia Sedona! Wrong customer!
Good job getting it sorted Aaron. Just for clartiy for future readers diagnosing a similar issue on the same model year vehicle, as has been mentioned that is GM Class 2 (J1850). It is a single wire serial data, network in star configuration, accessible at Splice Pack SP205. It toggles from 0v at rest to approximately 7 volts when active. With a Fluke 87 or similar, you'll see approximately…
Thank you for this very valuable information Martin! def will use this in info in the future
Aaron- do you really have 4 years experience? If so fantastic job bud! Youre way ahead of the game. Dont forget to get paid man. Once you have some more time under your belt, you can make reaally good money doing diag work.
Hey Rudy. Even only 1 good year of expertise beats out 30 years of bad experiences and no expertise any day! VBG. There's some truly smart and capable young guys and gals out there, despite the general BS and negativity that is put around about Millenials and Gen Z ("Zoomers").
Hi Arron , you was asking about training I will tell u ATG has the best training and their manuals are priceless they offer on line and in person classes all over country they have a communication class coming up in November on line HTH
Really nice work there getting it done. The video might come off as scattered, but I can follow it just fine. I've got a few case studies myself that I've wanted to post but I simply don't have the time to make up a nice presentation so I don't post them at all. Getting the information out there is the most important thing and you've done a great job doing just that!