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Thread: Fibre optics, circuit boards, and machine learning

  1. #1
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    Default Fibre optics, circuit boards, and machine learning

    2014 BMW 328d wagon F31

    The complaint that is written on the work order is very ambiguous and does not describe the problem very well. This happens a lot. After trying to comprehend what these few sentences mean, the Bluetooth and a few other media devices don't work intermittently, especially when it's raining. The vehicle has been to the dealer and another independent shop for this problem, and it's still not fixed. I go for a test drive, the radio is playing. After about 3 minutes I loose sound out of the speakers. This is the problem that we are going chase.

    How do we fix this? I have 1 hour to come up with a solution or a direction that leads to the solution.

    I start by performing a full vehicle trouble code scan. I want to see what systems are setting what faults.

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    I have to decide what codes I'm going to pursue. The no communication with the amplifier and instrument panel, and the MOST ring break are the ones that I'm going to focus on. The module (computer) topography shows the amplifier and the instrument panel are not communicating on the MOST network.

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    MOST stands for media oriented system transport. It is fibre optical data network. It connects modules together in series using plastic tubes (optical fibre). The optical fiber transmits light pulses in-between the modules. The light pulses are binary code. Light on is 1, light off is 0. MOST gets used for audio and video systems. It can move a shit load of data very quickly. This is a ring type network, that means the modules are connected in series in a big circle, and not parallel. If one of the modules stops communicating or there is a optical fiber problem, the whole network stops communicating. There is only one path and direction for the light to travel. The ring break code set because something caused an open in the network.

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    I'm using ISTA, this is the factory BMW scan tool. Once you identify the vehicle through ISTA, you are establishing an Ethernet connection in between the vehicle and BMW's servers. Automotive manufacturers are in the business of data collection. BMW is going to take full advantage of this situation and log, download, and save as much as they can from the vehicle and the diagnostic session. I have a trouble code for a ring break, I'm going to use a guided fault finding program. I click on the code and hit the calculate test plan button. Test plans will hold my hand and give me step by step instructions on how to diagnose this fault. I run the test plan for the ring break code, it tells me the MOST systems is fine. It's clearly not fine, the sound does not work, and I have two non-communicating modules. My one hour is up, I fill out the notes on the work order and recommend 3 more hours of diagnostic time.

    Later that day, I get approval for 2 more hours of time. I run the ring break test plan again. This time it tells me there is break, and it wants to re-start communication on the ring. I disconnect the negative battery cable for a few minutes then reconnect it. As the vehicle powers up, each module on the MOST network will send a message to the next module saying, who they are and if they are working properly. From this, the test plan will try to narrow down the ring break in between two modules. But, I get this:

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    When performing test plans, they produce a lot of diagnostic data. This data gets used to train machine learning programs. Neural Networks get used a lot in automotives.
    https://en.m.wikipedia.org/w/index.p...&diffonly=true
    Automotive manufacturers have been trying to replace technicians with a cheaper alternative for a few decades now. Their thought process is; get current expensive technicians to generate data so we can train a AI system to do their job a lot cheaper.

    Now, let's do a bunch of shit a software program cannot do. There is only three modules on this MOST network. I have to gain access to all of them. I'm not going to fully remove them, I just want access to their electrical connectors. I remove the instrument panel out of the dash. I remove the head unit also out from the dash. The amp sits in the left rear corner of the trunk. The fibre optical cable has a green casing on it, they kinda look like thick green wires. Each module has a connector with two optical cables. On the connectors, terminal 1 is incoming light, terminal 2 is outgoing light. I unplug the optical connector off of all three modules. I take my flashlight and shine it down terminal 2 at the head unit. I get a bright white light at terminal 1 at the instrument panel. A dim or no light would indicate a problem. This leg of optical cable is good. I check each leg of the network, and all optical lines are good. All of the connections in between the modules are ok, the chances of a module it's self causing the ring break is now very high.

    We are going to start removing modules out of the network until we find what one is causing the ring break. I can't just unplug the optical connector, that will cause another open. I un-plug the connector, on the vehicle side, I plug in a fiber optic jumper connector.

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    This removes the module out of the network but closes the open circuit the module left. The head unit is the master module, it is in charge of running the network so you can't remove that one. That leaves us with the instrument panel and the amplifier. The amplifiers have a high failure rate so I'm going to start there. I remove the amp from the network, then using the scan tool, I do a full vehicle trouble code scan.

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    The amp still doesn't have communication, because it's not even connected to the network. But, I have now gained communication with the instrument panel. The amplifier is causing the MOST ring break. The amplifier is receiving communication but not sending any to the head unit. I check all of the amplifiers powers and grounds. They all have appropriate voltages and are able to carry a load. The failure is internal to the amp. I remove it from the vehicle and unscrew the case. I remove the main circuit board with two other boards attached to it. I have a magnifying glass and a good bright light. I throughly inspect both sides of all the boards. I'm looking for any type of liquid staining. Any type of conductive liquid that gets on this circuit board will fuck it right up. Any cracked soldering joints. Any burnt or leaking components on the board. I don't find anything. Most times I don't find anything but will find liquid staining the most, sometimes a burnt diode or resistor or a leaking capacitor. I recommend replacing and programming a new amplifier.

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    A few days later a new amp shows up. I've got a bunch of jobs on the go, the amp install goes to another technician. I work for an independent shop and everyone is paid hourly, my job being given to another technician is no big deal. If this was flat rate dealership world, I would walk into the service managers office and initiate an unpleasant conversation, that MF is not going to give my job to someone else. Three hours were billed for this diagnostic job, I spent 4. I'm -1 hour. I need to make that time up on the install or I would be working an hour for free. Flat rate forces technicians to be assholes that have to look out for themselves. Instead, I'm paid the same amount even though I billed -1 hour. My employer ate the -1, had harmony in the shop, still made good profit, and got the satisfaction/reputation of fixing a vehicle two of his competitors couldn't.

    Programming and coding in a new amp is a topic all on its own, so I won't really go into that. After the new amp is set up, the vehicle has sound again, the Bluetooth and all of the media functions all work properly. And now I have communication with all modules. I'm not sure what the final bill was, it was probably few thousand dollars.

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    Humans = 1
    Artificial intelligence = 0

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    Another $3000 job in the books. Nice fix and good thing ista is pretty good at laying the systems out for a tech now. Not like inpa.

    Damn these newer vehicles and so complex. Once the screens start failing in the newer ones, we'll look like Cuba because who will afford paying $3k-$8k on a $10k vehicle?

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    Quote Originally Posted by mr2mike View Post
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    Another $3000 job in the books. Nice fix and good thing ista is pretty good at laying the systems out for a tech now. Not like inpa.

    Damn these newer vehicles and so complex. Once the screens start failing in the newer ones, we'll look like Cuba because who will afford paying $3k-$8k on a $10k vehicle?
    I think INPA is obsolete field service engineer software. It should have been used to install experimental software. It not going to be an easy program to navigate.

    It's interesting, I regularly do repairs on vehicles the come close to or exceed the value of the vehicle. Not every one wants vehicle payments or the hassle of replacing the vehicle. The cost of the repair is only one factor. Finding a competent technician that can diagnose and repair the problem and finding parts are generally bigger factors than how much it costs.

    Finding parts is a big one. Used modules is a interesting world. Programming with aftermarket software and cloning modules. Board level repair is starting to happen in some shops, I'm kinda on the fence if I want to get into that world or not.

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    You are one damn good tech. We could use a guy like you at our dealership if u ever think about coming to Edmonton.
    Originally posted by GTS Jeff
    You know those bored stay at home moms who's entire lives revolve around driving their kids to soccer, various cleaning accessories, and worrying about neighbourhood rapists? The kind of people that watch the View and go "uh huh..." Those unfulfilled people who try to fill the void in their empty lives by writing whiny letters to the editor complaining about shit that no one really cares about?

    Well imagine if instead of writing that letter to the editor, she just posts on a car forum for car enthusiasts. That's Kritafo.

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    Quote Originally Posted by mr2mike View Post
    This quote is hidden because you are ignoring this member. Show Quote
    Damn these newer vehicles and so complex. Once the screens start failing in the newer ones, we'll look like Cuba because who will afford paying $3k-$8k on a $10k vehicle?
    Is that's the issue with out of warranty 5/7 series and E/S classes? Friend bought his dad a 20 year old S class to check off bucket list for cheap, biggest mistake ever.

    Can't get rid of it quick enough.

    And if we ever let Chinese brands get in here, I'm sure cars will be priced to be disposable anyway.

    Quote Originally Posted by Flexray View Post
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    It's interesting, I regularly do repairs on vehicles the come close to or exceed the value of the vehicle. Not every one wants vehicle payments or the hassle of replacing the vehicle. The cost of the repair is only one factor. Finding a competent technician that can diagnose and repair the problem and finding parts are generally bigger factors than how much it costs.
    The older I get, the more I hate new cars. I won't oppose to paying a bit to extend life of old ones.
    Last edited by Xtrema; 07-02-2024 at 11:58 AM.

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