> Turns out that actual cars don’t have individual cables. Instead they have these big “looms”, which bundle many cables from a nearby area into a single harness. This is the reason why I could not find the individual cable earlier. They simply don’t manufacture it.
I was really surprised to read this at the end of the article -- how could someone be this deep into a project of this depth and not realize this?! Not only because all cars (...er... all vehicles) are wired this way, but also because the documentation they were referencing has plenty of detail to show this... there's even a whole picture of it (and to Tesla's credit they have amazing free docs): https://service.tesla.com/docs/Model3/ServiceManual/2024/en-...
Software people tend to overestimate their knowledge of other disciplines, writing it off as "easy" or work beneath them. Being overpaid compared to your peers certainly doesn't help dispel this feeling. Some people have built entire careers around designing wire looms.
Even if you know that cars consist of a single wiring harness, it's not implied that they aren't modular and the individual cables cannot be purchased separately.
Anyone with a modicum of knowledge about cars or wire looms already knows this is how it's done. So, anyone with legitimate business in the discipline.
Does everything need to be documented at a third-grade level in case some software person decides he wants to power up car parts on a table so he can write a blog post?
Cars usually consist of multiple harnesses -- as it is in this case as well. The harnesses are the cables in a car. That is the part you can purchase because that is the part.
I will say I’m surprised how far apart the two boxes are in the car. I guess they’re not where I thought. I would assume they’re both up near the dash.
The passenger side kick panel or behind the glove box are two very common places for vehicle computers -- some cars have them under the hood, which I always thought was a bad idea.
My RAM truck with the Cummins diesel engine has the engine computer mounted on the engine block. You'd think the heat and exposure to the elements would make that a bad idea, but I suppose Cummins knows what they're doing.
I used to work for a company that made third party scan tools. We had racks of ecus disconnected from the car with just a diagnostic connector and power. nothing got to a real car without first trying it on the rack. I remember on time we figured out a bmw (pre obdii) had the bytes offset from the standard documentation (it was a semi-standard protocol that some other cars used at the time), we went from we communicate but nothing is wrong to a very long list of dtcs on that controller. (All our competitors also showed nothing wrong, but the official bmw tool showed dtcs)
Congrats, OP has recreated a test/development bench, the bane of developers working on automotive software development all around the world. They're so close to being a real vehicle that you think you'll be able to get a lot of work done, but they're not, so you don't.
Honestly I love it. Few things develop a more fun camaraderie than a bringup bootcamp with two precious/priceless new samples on a large conference table, and everyone being very careful to keep cups/mugs very far away.
And a soldering robot with a specialist a few rooms away to beam down the latest errata into physical form, at times.
Tracy Kidder just died, and Soul of a New Machine was a favorite of my formative years as an engineer. Once I started in headunit ECU development it felt very familiar to me at times.
I'm a software guy, but the gear has a lot of allure.
It's funny to hear LVDS be described as an "automotive" cable when all of my run-ins with it are for connecting laptop displays to their main-boards! (though that has a very different connector on it, and its a very general term for the signalling protocol from what I remember)
Not saying there's anything wrong with your perspective (lots of terms get in muddied waters, it's common and not a problem if everyone is on the same page), but this is what I just found on Wikipedia:
"Early on, the notebook computer and LCD vendors commonly used the term LVDS instead of FPD-Link when referring to their protocol, and the term LVDS has mistakenly become synonymous with Flat Panel Display Link in the video-display engineering vocabulary."
The cable in the article is pretty much doing the same conflation of terms that Wiki is talking about - the automotive one is a proprietary cable that carries some protocol that uses LVDS as its signalling, so at the most basic level both it and the display cable in the laptop are 'LVDS cables' but that's also the most generic term that gives you no information about the protocol actually being carried by the cables.
Yeah I saw that too which is why I posted my comment, it's surprising to me :) LVDS for display cables was an incredibly term in that context. Even still is sometimes despite them mostly being eDP (embedded-DisplayPort) now, which is quite incorrect hah
> A REST-like API on :8080 which returned a history of “tasks”
I am curious to know what kind of historical tasks- since it's a media control unit; does it show what kind of media was being played in the last trip? does it reveal any other info about the driver?? There might be a privacy angle here that you could exploit and share it with Tesla.
Hey, I just remembered my school used to have ages ago some cool power supplies (I think from Agilent?) that were very idiot proof, they had current limit with a dial that I think didn’t went over 1A or perhaps even less, and they would instantly disarm on short circuit (and indicate it with a led), and also the voltage dial I think wouldn’t go over 25V. I remember it was very big and heavy, but it survived countless students that used the lab daily.
Nowadays, is there any power supply available that is that resistant or is the recommended approach to get an used old one? Does anyone have a power supply at home that is also used by kids with a brand/model they would recommend? Thanks!
What you're describing is a lab power supply. (The "instantly disarm on short circuit" is overcurrent protection, which is a standard feature.) The name brands like Keysight or Rigol are kind of expensive, but there are a lot of no-name models on Amazon which will do the job well enough.
Very cool. Over a year and a half ago I installed a towing brake controller in my Tesla Model Y. Found the location of the plug, how to access and the pinout online (confirmed via a voltmeter..) so the car's side felt straight forward. But then I needed to find a brake controller that can work with the higher voltage (14.4v vs the normal 12v). Then built a cable from the brake controller to the connector that plugs into the car that I found on eBay. I velcro'd the controller under the dashboard. It works pretty well. I towed my small camper several times with it last year with no issues. Yay! However my little project is nothing compared to this post. Love people hacking away. So cool.
>then I needed to find a brake controller that can work with the higher voltage (14.4v vs the normal 12v)
Put a voltmeter on the battery terminals of a regular car at 2000rpm and note the voltage. You'd be surpised (the alternator can produce as high as 15V on some cars).
Automotive transients can be wild. I did a bringup with a board that had specified 100+v range specified for transients and finicky quality requirements on the output. The power supplies took up most of the (very large) board.
14v is not a transient, if your voltage was 12v with the car running, there's something wrong with the charging system (DC-to-DC in an EV, alternator/generator in an ICE)
13-14v is normal in all 12v automotive systems as the charging voltage
If I recall correctly, a fully charged lead acid battery has an open circuit voltage of 13.6V.
So the alternator has to put out at least something higher than if it’s planning on recharging the battery after 500 to 700 amps have been pulled from it for a few seconds to start the engine.
I typically fault anything above 15.6V as “that’s a bit high, your alternator might be on its way out” when working on automotive / caravan / camper van appliances and accessories.
you're correct. a '12v ICE' alternator generates up to 14.8-15.2v. Most automotive stuff can operate between 9ish-16ish-v , of course totally depending on the product.
of course this is just a modern interpretation. older stuff runs at 6v and some weirdo offbeat cars have a 24v/48v rail sitting around somewhere. Cop cars often had alternators that put out weird voltage ranges for certain equipment, or dual 12v for high amperage output.
Even just a "12v" automotive battery itself is mostly dead if if actually reads 12.0V. Fully charged is around 12.6 or 12.7. If a car had an electrical system that actually ran at 12 volts, the battery would always be dead.
"12v" in reference to anything automotive is very much a nominal reference.
> Whilst cranking, an ICE car will drop to around 6 volts (then maximum power is extracted according to thevenim's theorem).
> That means all computers etc will work at 6v.
Not necessarily all of them. Plenty of stuff will drop out while cranking; hopefully not the computers that run the fuel injection and ignition, though.
The specs say no less than 6volts. In the real world when the temperature drops down to -70F or colder and batteries get old the voltage goes well below that: deal with it.
You are probably right. Surprisingly the first controller I tried didn't work. I assumed the voltage was too high since it worked in my other (much older) car. I found a reference online of people that tried a particular brand/model and that's what I went for. Thankfully my car isn't the model with the internal 18v battery.
People need to request the source code.. There’s a ton of open source they use that forces Tesla to give you source if you’re a customer and you ask. I don’t get why security people aren’t doing this already.
I _do_ find it weird that the LCDs from crashed cars are so expensive. I wonder if newer models have better screens, so people with older cars upgrade? Or if they're a common failure point?
I have a Model 3, but I can't say I follow the forums.. but I've never heard of screens failing -- I'm sure it happens but I think if it was common problem I'd have heard of it.
I'd guess they fail not on their own, but because they are human interface devices and take the brunt of abuse... e.g. iPhone screens are a popular repair despite being reliable components.
Some newer models have better (bigger) screens, and some are incompatible since they've slightly changed the connector. Old models (pre highland/ jupiter facelift) have used the same display shown in the article for a very long time across M3 and MY. What usually happens is that they physically break because people are not that careful, so the touch screen ends up breaking - although you really have to put a lot of force to break that display.
My 2016 Model S LCD panel developed the well-known fault of delamination and leaking some kind of sticky fluid.
Turns out the early Model S vehicles used consumer grade LCD panels that weren’t designed for the prolonged high heat you get in a metal and glass box left outside in the sun all day.
Tesla since upgraded their vehicle screens to proper automotive-grade LCDs which are excellent.
My point is, automotive-grade hardware is higher spec than regular consumer computer hardware, hence the high prices.
As an aside, I upgraded my whole computer and screen from MCU1 to MCU2 and it was worth the upgrade.
Credit to Tesla for building a retrofit computer upgrade for old vehicles. Thats a non-trivial thing to engineer and I appreciate their effort. Other car manufacturers would prefer you were compelled to buy their latest vehicle instead.
i wish the ui on those things was more visually appealing. between the cheap looking gloss finish on the display itself and the unextraordinary ui, it's just kinda blah. one can have a debate about to screen or not to screen or whether to use vfd displays or whatever and i get the importance of cost control but it should look good and it really doesn't. the graphic of the car looks like a cartoon.
Granted, I think it would be valuable to look at all sorts of automotive ECUs. I always wonder how the tuning industry does their thing; I shudder to think they're just sitting there flipping hex codes directly in running software...
I'm amused reading the terms and requirements the author mentions in the bug bounty program for researchers gaining root access (under 'Vehicle Targets') - https://bugcrowd.com/engagements/tesla
"To promote further security research, Tesla offers security researchers the opportunity to retain root access on their infotainment system even after their reported vulnerability has been patched. In order to qualify, a researcher must send in a valid report describing a novel way to gain root access on a Tesla infotainment system. Upon confirmation, Tesla will instruct the researcher on how to use their existing root access to enable the researcher SSH feature, along with an SSH certificate for the researcher's public key (tailored to their specific hardware ID). The certificate restricts SSH access to the local diagnostic ethernet link. Tesla may renew the certificate as long as the researcher continues reporting vulnerabilities."
Ha! Reading this comment made me curious, so I went back and looked at the article and there does seem to be a full sized HDMI connector. I wonder if it is enabled, or just for Tesla internal testing?
It actually stands for "lizard brain"... it is (or at least was) an Infineon Aurix control and monitoring microcontroller, they may have changed to a newer one.
> Turns out that actual cars don’t have individual cables. Instead they have these big “looms”, which bundle many cables from a nearby area into a single harness. This is the reason why I could not find the individual cable earlier. They simply don’t manufacture it.
I was really surprised to read this at the end of the article -- how could someone be this deep into a project of this depth and not realize this?! Not only because all cars (...er... all vehicles) are wired this way, but also because the documentation they were referencing has plenty of detail to show this... there's even a whole picture of it (and to Tesla's credit they have amazing free docs): https://service.tesla.com/docs/Model3/ServiceManual/2024/en-...
Software people tend to overestimate their knowledge of other disciplines, writing it off as "easy" or work beneath them. Being overpaid compared to your peers certainly doesn't help dispel this feeling. Some people have built entire careers around designing wire looms.
> how could someone be this deep into a project of this depth and not realize this
I think this is a software guy who occasionally dips into hardware things (to hunt bugs).
That's what I figure -- but it was wild to read that after reading the part about component-level PCB repair lol
[delayed]
Even if you know that cars consist of a single wiring harness, it's not implied that they aren't modular and the individual cables cannot be purchased separately.
First, cars don't consist of a single harness.
Second, why would it be implied?
Anyone with a modicum of knowledge about cars or wire looms already knows this is how it's done. So, anyone with legitimate business in the discipline.
Does everything need to be documented at a third-grade level in case some software person decides he wants to power up car parts on a table so he can write a blog post?
Cars usually consist of multiple harnesses -- as it is in this case as well. The harnesses are the cables in a car. That is the part you can purchase because that is the part.
There's a list of them here: https://service.tesla.com/docs/Model3/ServiceManual/2024/en-...
I will say I’m surprised how far apart the two boxes are in the car. I guess they’re not where I thought. I would assume they’re both up near the dash.
The passenger side kick panel or behind the glove box are two very common places for vehicle computers -- some cars have them under the hood, which I always thought was a bad idea.
My RAM truck with the Cummins diesel engine has the engine computer mounted on the engine block. You'd think the heat and exposure to the elements would make that a bad idea, but I suppose Cummins knows what they're doing.
I used to work for a company that made third party scan tools. We had racks of ecus disconnected from the car with just a diagnostic connector and power. nothing got to a real car without first trying it on the rack. I remember on time we figured out a bmw (pre obdii) had the bytes offset from the standard documentation (it was a semi-standard protocol that some other cars used at the time), we went from we communicate but nothing is wrong to a very long list of dtcs on that controller. (All our competitors also showed nothing wrong, but the official bmw tool showed dtcs)
Diagnostic Trouble Codes?
Congrats, OP has recreated a test/development bench, the bane of developers working on automotive software development all around the world. They're so close to being a real vehicle that you think you'll be able to get a lot of work done, but they're not, so you don't.
Honestly I love it. Few things develop a more fun camaraderie than a bringup bootcamp with two precious/priceless new samples on a large conference table, and everyone being very careful to keep cups/mugs very far away.
And a soldering robot with a specialist a few rooms away to beam down the latest errata into physical form, at times.
Tracy Kidder just died, and Soul of a New Machine was a favorite of my formative years as an engineer. Once I started in headunit ECU development it felt very familiar to me at times.
I'm a software guy, but the gear has a lot of allure.
It's funny to hear LVDS be described as an "automotive" cable when all of my run-ins with it are for connecting laptop displays to their main-boards! (though that has a very different connector on it, and its a very general term for the signalling protocol from what I remember)
Not saying there's anything wrong with your perspective (lots of terms get in muddied waters, it's common and not a problem if everyone is on the same page), but this is what I just found on Wikipedia:
"Early on, the notebook computer and LCD vendors commonly used the term LVDS instead of FPD-Link when referring to their protocol, and the term LVDS has mistakenly become synonymous with Flat Panel Display Link in the video-display engineering vocabulary."
https://en.wikipedia.org/wiki/Low-voltage_differential_signa...
The cable in the article is pretty much doing the same conflation of terms that Wiki is talking about - the automotive one is a proprietary cable that carries some protocol that uses LVDS as its signalling, so at the most basic level both it and the display cable in the laptop are 'LVDS cables' but that's also the most generic term that gives you no information about the protocol actually being carried by the cables.
Yeah I saw that too which is why I posted my comment, it's surprising to me :) LVDS for display cables was an incredibly term in that context. Even still is sometimes despite them mostly being eDP (embedded-DisplayPort) now, which is quite incorrect hah
SpaceWire is also just LVDS with an uber-minimal routing protocol. It runs on a lot of satellites.
Interesting.
> A REST-like API on :8080 which returned a history of “tasks”
I am curious to know what kind of historical tasks- since it's a media control unit; does it show what kind of media was being played in the last trip? does it reveal any other info about the driver?? There might be a privacy angle here that you could exploit and share it with Tesla.
> A DC power supply capable of providing 12V
Hey, I just remembered my school used to have ages ago some cool power supplies (I think from Agilent?) that were very idiot proof, they had current limit with a dial that I think didn’t went over 1A or perhaps even less, and they would instantly disarm on short circuit (and indicate it with a led), and also the voltage dial I think wouldn’t go over 25V. I remember it was very big and heavy, but it survived countless students that used the lab daily.
Nowadays, is there any power supply available that is that resistant or is the recommended approach to get an used old one? Does anyone have a power supply at home that is also used by kids with a brand/model they would recommend? Thanks!
What you're describing is a lab power supply. (The "instantly disarm on short circuit" is overcurrent protection, which is a standard feature.) The name brands like Keysight or Rigol are kind of expensive, but there are a lot of no-name models on Amazon which will do the job well enough.
Those were called something like desktop power supplies.
https://www.mouser.com/c/power/power-supplies/power-supplies...
AT $5k it better make me breakfast, too.
They have variable dc power supplies on amazon on the cheap.
If you want that sort of reliability it will probably go towards 100$.
Very cool. Over a year and a half ago I installed a towing brake controller in my Tesla Model Y. Found the location of the plug, how to access and the pinout online (confirmed via a voltmeter..) so the car's side felt straight forward. But then I needed to find a brake controller that can work with the higher voltage (14.4v vs the normal 12v). Then built a cable from the brake controller to the connector that plugs into the car that I found on eBay. I velcro'd the controller under the dashboard. It works pretty well. I towed my small camper several times with it last year with no issues. Yay! However my little project is nothing compared to this post. Love people hacking away. So cool.
>then I needed to find a brake controller that can work with the higher voltage (14.4v vs the normal 12v)
Put a voltmeter on the battery terminals of a regular car at 2000rpm and note the voltage. You'd be surpised (the alternator can produce as high as 15V on some cars).
Automotive transients can be wild. I did a bringup with a board that had specified 100+v range specified for transients and finicky quality requirements on the output. The power supplies took up most of the (very large) board.
14v is not a transient, if your voltage was 12v with the car running, there's something wrong with the charging system (DC-to-DC in an EV, alternator/generator in an ICE)
13-14v is normal in all 12v automotive systems as the charging voltage
If I recall correctly, a fully charged lead acid battery has an open circuit voltage of 13.6V.
So the alternator has to put out at least something higher than if it’s planning on recharging the battery after 500 to 700 amps have been pulled from it for a few seconds to start the engine.
I typically fault anything above 15.6V as “that’s a bit high, your alternator might be on its way out” when working on automotive / caravan / camper van appliances and accessories.
> But then I needed to find a brake controller that can work with the higher voltage (14.4v vs the normal 12v)
Not understanding this sentence. Most running ICE vehicles product closer to that 14.4 than 12v. I think a standard controller would have worked fine?
you're correct. a '12v ICE' alternator generates up to 14.8-15.2v. Most automotive stuff can operate between 9ish-16ish-v , of course totally depending on the product.
of course this is just a modern interpretation. older stuff runs at 6v and some weirdo offbeat cars have a 24v/48v rail sitting around somewhere. Cop cars often had alternators that put out weird voltage ranges for certain equipment, or dual 12v for high amperage output.
Even just a "12v" automotive battery itself is mostly dead if if actually reads 12.0V. Fully charged is around 12.6 or 12.7. If a car had an electrical system that actually ran at 12 volts, the battery would always be dead.
"12v" in reference to anything automotive is very much a nominal reference.
Whilst cranking, an ICE car will drop to around 6 volts (then maximum power is extracted according to thevenim's theorem).
That means all computers etc will work at 6v.
> Whilst cranking, an ICE car will drop to around 6 volts (then maximum power is extracted according to thevenim's theorem).
> That means all computers etc will work at 6v.
Not necessarily all of them. Plenty of stuff will drop out while cranking; hopefully not the computers that run the fuel injection and ignition, though.
The specs say no less than 6volts. In the real world when the temperature drops down to -70F or colder and batteries get old the voltage goes well below that: deal with it.
You are probably right. Surprisingly the first controller I tried didn't work. I assumed the voltage was too high since it worked in my other (much older) car. I found a reference online of people that tried a particular brand/model and that's what I went for. Thankfully my car isn't the model with the internal 18v battery.
You can run QtCar (the Qt-based app that Tesla uses for their UIs) on QEMU - if you have the firmware.
https://x.com/i/status/1722717318009041104
DM me if interested
People need to request the source code.. There’s a ton of open source they use that forces Tesla to give you source if you’re a customer and you ask. I don’t get why security people aren’t doing this already.
I _do_ find it weird that the LCDs from crashed cars are so expensive. I wonder if newer models have better screens, so people with older cars upgrade? Or if they're a common failure point?
I have a Model 3, but I can't say I follow the forums.. but I've never heard of screens failing -- I'm sure it happens but I think if it was common problem I'd have heard of it.
I'd guess they fail not on their own, but because they are human interface devices and take the brunt of abuse... e.g. iPhone screens are a popular repair despite being reliable components.
Some newer models have better (bigger) screens, and some are incompatible since they've slightly changed the connector. Old models (pre highland/ jupiter facelift) have used the same display shown in the article for a very long time across M3 and MY. What usually happens is that they physically break because people are not that careful, so the touch screen ends up breaking - although you really have to put a lot of force to break that display.
My 2016 Model S LCD panel developed the well-known fault of delamination and leaking some kind of sticky fluid.
Turns out the early Model S vehicles used consumer grade LCD panels that weren’t designed for the prolonged high heat you get in a metal and glass box left outside in the sun all day.
Tesla since upgraded their vehicle screens to proper automotive-grade LCDs which are excellent.
My point is, automotive-grade hardware is higher spec than regular consumer computer hardware, hence the high prices.
As an aside, I upgraded my whole computer and screen from MCU1 to MCU2 and it was worth the upgrade.
Credit to Tesla for building a retrofit computer upgrade for old vehicles. Thats a non-trivial thing to engineer and I appreciate their effort. Other car manufacturers would prefer you were compelled to buy their latest vehicle instead.
> Unfortunately I had no other choice but to buy this entire loom for 80 USD.
Fwiw, mine costs $450 from Ford. Also in the US we call this a wiring harness, with the loom being the material that goes over the wires
i wish the ui on those things was more visually appealing. between the cheap looking gloss finish on the display itself and the unextraordinary ui, it's just kinda blah. one can have a debate about to screen or not to screen or whether to use vfd displays or whatever and i get the importance of cost control but it should look good and it really doesn't. the graphic of the car looks like a cartoon.
"tuner" almost certainly refers to a radio (think AM/FM/SiriusXM) tuner module
Granted, I think it would be valuable to look at all sorts of automotive ECUs. I always wonder how the tuning industry does their thing; I shudder to think they're just sitting there flipping hex codes directly in running software...
I'm amused reading the terms and requirements the author mentions in the bug bounty program for researchers gaining root access (under 'Vehicle Targets') - https://bugcrowd.com/engagements/tesla
"To promote further security research, Tesla offers security researchers the opportunity to retain root access on their infotainment system even after their reported vulnerability has been patched. In order to qualify, a researcher must send in a valid report describing a novel way to gain root access on a Tesla infotainment system. Upon confirmation, Tesla will instruct the researcher on how to use their existing root access to enable the researcher SSH feature, along with an SSH certificate for the researcher's public key (tailored to their specific hardware ID). The certificate restricts SSH access to the local diagnostic ethernet link. Tesla may renew the certificate as long as the researcher continues reporting vulnerabilities."
Very neat.
I have no wheels and I must drift
I love that it has a standard RJ45 ethernet connector.
I thought I saw an HDMI connector, but maybe I was wrong.
Ha! Reading this comment made me curious, so I went back and looked at the article and there does seem to be a full sized HDMI connector. I wonder if it is enabled, or just for Tesla internal testing?
It's only a debug port and not actually HDMI signaling, unfortunately.
How many PoE adapters would it take to charge a Tesla?
Mostly depends on how fast you want to charge.
Could 'lb' be load balancer?!
It actually stands for "lizard brain"... it is (or at least was) an Infineon Aurix control and monitoring microcontroller, they may have changed to a newer one.
Fun linguistic quirk: Americans tend to call it a "wiring harness", whereas Brits prefer "loom"
So what do you call the tubing around the wire bundle? That’s what we call “loom”.
In Canada we generally call it the sleeve, or the wrap.
I'd understand either of those, but I'd go with "tubing"
https://www.3m.com/3M/en_US/p/c/electrical/wire-cable/tubing...