Any Open Source Solutions For DIY Auto Diagnostics? 270
slaxx writes "As an avid tinkerer, I really want to collect as much data about my car as possible. Using On-Board Diagnostics (OBDII) sounded great to me, but the pricetags of systems like AutoTap Scanner are a bit much for my college budget to handle. Are there any free, open source solutions available? What do Slashdotters do to tinker and record the inner workings of their own vehicles?"
To Expensive? (Score:2, Insightful)
If $199 is to expensive for the hardware and software onyour Budget what do you expect to be able to fix on the car for cheaper?
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Thats true: you can always get something cheap like this:
http://www.gridconnect.com/canusblight.html [gridconnect.com]
Which is like $99 and it will work fine but you lose out on getting stuff like CAN monitors, API's and programming examples with the better adapters... Your best bet is to go with something like this:
http://www.gridconnect.com/usbcanin.html [gridconnect.com]
which is a full featured adapter that you can actually do development and project work with.
Re:To Expensive? (Score:4, Informative)
I have an older version of this:
http://www.sctflash.com/X3.php [sctflash.com]
It reads codes, but also allows me to Upload new profiles to my cars' EEC.
A warning: You can really fuck up your car with one of these, as the learning curve is pretty steep.
But being able to vary tuning setups is almost a requirement on older (late 90's) cars with obdii.
An example: The 03 PI engine going into my car has completely different tuning specs than the old engine; it will run, but will run MUCH better with a new tune.
The DOHC version has even more different tuning curves...
The only part of it I hate is the fucking encryption the government insisted on, to keep us out of the eec. That always works, lol.
Re:To Expensive? (Score:4, Informative)
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If $199 is to expensive for the hardware and software onyour Budget what do you expect to be able to fix on the car for cheaper?
Something that would be $199 cheaper having not had to pay for software and hardware.
Re: Too Expensive? (Score:4, Insightful)
Currently you need a specially-adapted laptop, a highly proprietary cable, and some very expensive software. Garages can afford this: individuals can't.
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It depends on what you're resetting. If it's the MIL you're wanting to reset, that may be accomplished with a simple OBDII reader that places like Wal-Mart and most reputable auto parts places will sell you for about $60-90. You're going to find that it'll cost more to read CAN or the other protocols than it's worth if all you're looking for is reset capability.
However, if you're into tinkering and are looking for understanding the OBDII or a base platform for getting it into your laptop, you'll spend $20
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I don't want to tinker, but if I fix something simple like an air filter, I want to be able to reset the console warning lights.
If you just want to be able to read diagnostic codes and reset the warning light(s), at most you need a standalone OBDII device, not a laptop, special hardware and software. Harbor Freight has them for US$50 right now [harborfreight.com], and I got one on sale there for about $30.
The only reason I know of to go the laptop route is to get detailed engine data like an emissions-testing station or perfor
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If that is all you want AutoZone/AdvanceAuto will usually reset the lights and read the codes for free. They'll try and sell you the part to fix it, but they don't force you to buy it.
I use VCDS [ross-tech.com] on my VW because when I'm diagnosing a problem on my car, I don't want to simultaneously diagnosing my tools.
It takes time and money to reverse stuff. There have been a few open source projects, but all stalled or weren't kept up to date. I see there's a new VW project on SF.
And as far as development goes, don't ask
Re:To Expensive? (Score:5, Informative)
More that you might expect.
Last three items that my PC based and inexpensive OBD-II diagnostics helped me diagnose on my cars were:
1. Poor connection at O2 sensor, cleaned connector cost $0.00
2. Bad water temp sensor, $15.00
3. Loose hose on air intake. Found because MAF readings were out of range. $0.00
I could have eventually fixed any of those without the OBD-II reader but it would have taken a lot more time to find the problem, or I could have bent over in front of some dealer service adviser and grabbed my ankles like a typical consumer and paid some big dollars.
The OBD-II codes didn't tell me exactly what to fix/replace on any of those but it greatly reduced trouble shooting time.
Also Google the codes the OBD-II spits out, odds are your car isn't the first with the problem. On item 2, Google told me that the water temp sensor had a high failure rate so I started there. A simple ohmeter check told me my sensor was dead.
Info for nervous Nellies, simple OBD-II readers are read only, so don't get your knickers in a knot.
Re:To Expensive? (Score:5, Insightful)
"The OBD-II codes didn't tell me exactly what to fix/replace on any of those but it greatly reduced trouble shooting time."
THIS. Yes, IN CAPS.
Scanners and shop scopes are GREAT for locating problems, but they do NOT replace a well-trained mechanic. Above poster makes it sound simple, but he already had an understanding of automotive tech. For example, using out-of-spec MAF readings to diagnosis an intake leak is one thing, but those readings could also be caused by intake valve issues, worn piston rings or a plethora of other things including a bad MAF sensor.
My point is that an understanding of the underlying systems is still required.
Don't expect a scanner, or even the information provided by one, to "fix" your car. They simply point you in the right direction (sometimes) and also allow you to verify the repair worked as planned.
A side point. A cheap scanner will never have a "snap-shot" function, while a decent one will. This is CRUCIAL in diagnosing intermittent failures. Otherwise, you will be sitting there trying to make the problem occur while you have the scanner hooked up, often missing the 20ms failure. Blink and you miss it. A good scanner will store "frames" of info to go back and examine.
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bad idea (Score:2, Insightful)
I'm all for tinkering, and tinkering with cars used to be a great hobby. But tinkering with proprietary chip sets - with consequences not only your driving experience, but on the safety of others around you - without the proper equipment strikes me as a uniquely bad idea.
Re:bad idea (Score:5, Informative)
http://diyefi.org/ [diyefi.org]
Get rid of the proprietary crap and tinkering can be just as much fun!
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Who cares about the proprietary chipsets when there are ISO standards for gathering data from them?
http://en.wikipedia.org/wiki/On-board_diagnostics#Standard_interfaces [wikipedia.org]
There have been mandatory standards for over 10 years, if only to make emissions testing faster by allowing the VEIP to plug directly into the OBD-II / CAN port under your dash to get emissions readings right from your engine instead of having to hook up that chemical analyzer to your exhaust.
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Tinkering? The whole point of these scanners is to read information and help diagnose problems.
He could do more harm to the "safety of others around" him by advancing the ignition curve, leaning out the mixture, and melting the piston crowns. Or - if he had less sense and went about it the wrong way - working on the assumption that more fuel = more pwer, thereby flooding the followers on the road with a stream of unburnt fuel.
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Also, the chips might be propriety but the connection and the codes/protocol are standard.
I guess he could screw up and read the code for brake-system-will-not-maintain-pressure as gas-cap-loose but in general I don't see how it could pose much of a threat to anyone.
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Here's an example: http://en.wikipedia.org/wiki/On-board_diagnostics#OBD-II_Signal_Protocols [wikipedia.org]
1. Complete nonsense; 2. google ELM327 (Score:3, Insightful)
I'm all for tinkering, and tinkering with cars used to be a great hobby. But tinkering with proprietary chip sets - with consequences not only your driving experience, but on the safety of others around you - without the proper equipment strikes me as a uniquely bad idea.
You've apparently got no understanding of what the OBD II interface lets you do.
OBD II lets you read trouble codes and operational data (sensor values, fuel integrator, ignition timing, etc.), and lets you clear trouble codes.
That's it. There's no danger at all. You can't alter anything other than clearing trouble codes.
To the original poster, google for "ELM327" to find the hardware, and "ELM327 software" to find software, including many free apps that will use the ELM interface to talk to OBD II.
I use a
Re:1. Complete nonsense; 2. google ELM327 (Score:5, Informative)
The radio in GM's (2001+) also don't have an accessory wire, it uses data as well which appears to also be tagged into the same CANbus. You must use a module to keep the factory chimes and create an accessory for you (you could just run your own ACC line but you lose all the features controlled via the radio over the data link). I've heard numerous times from other installers where an idatalink rem start/alarm module wouldn't program to a GM correctly with the aftermarket radio/adaptor installed. Unplug the adaptor, plug the factory radio in, and everything programs fine. So on some makes/models there's a lot more running over that CAN interface than you have any idea about.
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In unrelated news, a GM spokesman denies putting wholly unrelated features into the radio in order to encourage owners to upgrade by purchasing an OEM radio at approximately four to eight times the price of an equivalent aftermarket model.
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idatalink list for 2010 Chevy Colbolt [idatalink.com]
This is just using the features they provide for a remote start install. But you can really muck things up using just pin 2 of the OBD-II port on GMs. In fact you can make the whole car either A> not run properly or B> cause the car to shut down fairly easily via the CANbus.
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I'm all for tinkering, and tinkering with cars used to be a great hobby. But tinkering with proprietary chip sets - with consequences not only your driving experience, but on the safety of others around you - without the proper equipment strikes me as a uniquely bad idea.
And OBD2 port is just a serial port. Actually, there are several different types of OBD2 hardware interfaces, but they all follow the same basic protocol [wikipedia.org] from a software perspective. I understand we have Congress to thank for that much. The proprietary parts are the PIDs that manufacturers add for specific product lines but the basics are pretty consistent. Besides ... querying your vehicle's ECU in the precise manner in which it was designed to be queried hardly constitutes tinkering with a proprietary chi
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Re:bad idea (Score:4, Informative)
I guess the unimaginative trolls are out in force on a Sunday morning. Here's some inspiration:
http://www.mbworld.org/forums/off-topic/260385-awesome-mr2-carputer.html [mbworld.org]
http://www.carobd.com/ [carobd.com]
But yeah, agreed, the future is a dangerous place. Not everyone should dare tread there ;-)
Get a CAN bus analyzer. (Score:2, Informative)
It's the underlying protocol of OBD II.
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Was going to mention this, but glad to see someone beat me to it. It's really not that hard to make your own scanner, in fact when I was in high school(over 15yrs ago), we built our own OBDI/II computer diagnostic scanner for our shop, hooked upto an Amiga1000. And you're talking about a bunch of guys(and one girl); who knew nothing about computer programing at the time. Or the basic understanding of the system. But we could follow directions, and knew how to wire breadboards. If there's someone here o
OBD (Score:2, Informative)
Have an arduino board? (Score:5, Interesting)
When I have the time, i've been meaning to try something like this:
http://en.wikipedia.org/wiki/OBDuino [wikipedia.org]
Into my Car so I can get additional performance gagues + graphs. I have the Arduino board, and can solder things here and there, I've just never gotten around to it ....
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If you want to use it as a digital dash, don't. ATMegas can't reliably run at fast enough serial rates to pump out the data fast enough for a real dash display. With all the stuff you want to display you'll end up at 5-10 updates a second, which just sucks.
If you just want to futz around and see whats there before digging in, its fine.
Realistically though, you can get a ODB-II to RS232 protocol converter for $40 or so, which is probably about $10 more than you paid for your arduino and it'll work far bett
two things (Score:2)
hardware - http://www.amazon.com/Crescent-OBD2-Multi-Protocol-Diagnostic-Scanner/dp/B001MT0XPK/ref=sr_1_2?ie=UTF8&s=automotive&qid=1274012569&sr=8-2 [amazon.com]
software - pyodb2
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Try pyobd2 instead. It was typoed in the GP post.
http://sourceforge.net/projects/pyobd2/ [sourceforge.net]
scantool (Score:5, Informative)
Look at http://www.scantool.net/ [scantool.net] . I use a Scangauge II. I went through this same thing; in the end I decided that buying a scangauge gave me 90% of what I wanted, out of the box, without having a computer clutter up the driving area, and without spending weeks hacking up something that might work but then again might not.
obdii hw, sw (Score:3, Informative)
telecommute (Score:2)
Slashdotters telecommute, so the only vehicle is the comp..
RomRaider (Score:2)
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Right to Repair (Score:2, Informative)
Support your right to repair: http://www.eff.org/deeplinks/2009/05/right-repair-law-pro [eff.org]
Here's a few informational links (Score:2)
Here is a link to a forum thread with links to basic/starter info: http://www.mp3car.com/vbulletin/hardware-development/51772-class-2-data-bus-j1850.html [mp3car.com]
I know GM uses j1850 for their OBD-II/CAN setup. Some of the things that can be read off of pin 2 at the OBD-II connector include Tach signal, bypass the chip-in-key, control door locks (mostly on 2001 and up though some older ones apply as well), con
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http://www.intrepidcs.com/ [intrepidcs.com]
Go to Autozone (Score:3, Informative)
They'll read your ODB unit at no charge. Reason is, of course, they hope that you will then elect to buy the part(s) you need from them to fix it. Just go in and ask, they'll bring out a portable unit that reads the diag codes. They'll take that back to a computer, upload the results, and give you a printout.
autozone (Score:2)
but as has been said... if 99-199 is too much, then don't even think about trying to enter into this very expensive hobby.
even ultra low budget and open source solutions are more than $99, even if you build the ecu yourself like with older megasquirt systems [msefi.com]
Just go to Schucks/Checkers/O'Reilly (Score:2)
Most local auto part supply stores will happily loan you an OBDII diagnostic tool for free. I've done this many times to read fault codes out of my car. It may not be as sexy as rolling your own, but it meets your price requirement.
Neil
When (Score:2)
When will it be the Year of Linux on the blacktop?
Maemo, Nokia web pad, Carman software (Score:2)
I went with Carman [indt.org] for Nokia's Maemo platform and a generic Bluetooth scantool. The advantage of this setup is that the Nokia webpad serves as an in-car media player, GPS unit and car computer, providing me with real-time diagnostics, positioning and entertainment.
For fault diagnostics, I gave up in the end. At least for my car, (an Audi S8) it seems there are error codes that are manufacturer specific. Without a translation table, the error codes aren't particularly useful and I couldn't find any software
single time just go to Autozone. (Score:2)
Autozone will read and clear trouble codes for free. So if you just have a one time need, do that.
I don't tinker with critical systems (Score:2)
I only have one car and I can't afford to have it not working so I don't tinker with it. I certainly am interested but I cannot afford the downtime. I can do it vicariously by going to the shop and watching the mechanic.
I have a computer that I need for work and I don't tinker with that either. But on that front at least I can afford to have another that I can mess with.
Thermodynamics fascinates me too but not enough to start taking apart my refrigerator.
Good lord if my mechanic were ever like the ones t
A Short Survey of Linux Software Solutions (Score:2)
Scantool (Score:2)
True DIY (Score:3, Informative)
http://www.elmelectronics.com/obdic.html [elmelectronics.com]
Check out the ELM327 chip on that page.
$33, rs-232 control of the chip and the chip speaks to ODBII: ISO 15765-4 CAN, SAE J1850 PWM, SAE J1850 VPW, ISO 9141-2, ISO 14230-4 and SAE J1939 protocols
You set the chip up with what to monitor and/or control (Similar in style to sending AT commands to a modem) and then it does the work of giving you the data stream.
Build your own standalone test gear, with or without a PC interface.
Googling for "ODB-II Connectors" was how I found the jack ends with pins to solder to. They varied in price a bit so where I purchased from 2 years ago no doubt isn't the cheapest now.
Have fun
build your own (Score:2)
That's great (Score:3, Funny)
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Agreed. Open Source is not a magic bullet.
Re:As an engineer... (Score:5, Insightful)
No, the reality is that the reason the equipment is expensive is so that dealerships have a corner on the market. Post-sales service is one of the largest sources of dealership income. Which, if you think about it, is a truly sad state of affairs. Besides politicians, what is the one thing people are often most cynical about? It's auto dealerships. Because no matter how educated the average person gets about the way a vehicle works, a clever desk manager can always tell you the mechanic in the back plugged in a diagnostic and it said the "[techspeak] board indicated the [techspeak] [techspeak] has failed which [techspeaks] your ignition, and this is caused by road salt erosion of your [techspeak] which is obviously not covered under the warranty".
No, making the test equipment expensive, or otherwise keeping it out of reach of the public is not the answer to either the technical issue of vehicle "safety" or the PR issue of cynical consumers. The answer is open standards, common test equipment, and education. This just doesn't do anything for dealership income, that's all.
Re:As an engineer... (Score:5, Insightful)
Mechanics are often not even mechanics any more. They plug in the diagnostic and whatever it says is wrong, is what is wrong.
Speaking as a former mechanic, fuck you very much. OBD II codes serve to provide you a place to look, nothing more.
Say for example the code is a misfire on Cylinder 3. Great. Do you have any idea how many different things can cause a misfire? It could be the ignition coil...or the spark plug...or the throttle body being clogged...or it could be a freak-one time thing that can't be replicated...or it could be something entirely different. Same thing with an O2 sensor. Just because it says "O2 Sensor Three is reading incorrectly" doesn't necessarily mean the O2 Sensor is bad. You could have bad wiring, the air/fuel mixture could be throwing off the reading, the person could have just put bad gas in it, or again many other possibilities. Have fun diagnosing that electrical problem that keeps causing the ECU to think that your Crank Positioning Sensor is bad (causing it to throw a code and making the check engine light come on), when in fact the sensor itself is perfectly fine.
It's not as simple as just "this is broken, please replace it." Many dealerships do this, but real shops do not.
Because no matter how educated the average person gets about the way a vehicle works, a clever desk manager can always tell you the mechanic in the back plugged in a diagnostic and it said the "[techspeak] board indicated the [techspeak] [techspeak] has failed which [techspeaks] your ignition, and this is caused by road salt erosion of your [techspeak] which is obviously not covered under the warranty".
If you go somewhere in which the guy up front tells you that, you demand that they put your car back together, take it off the rack, and go somewhere else. You didn't take your car to a shop, you took it to a lie.
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If you go somewhere in which the guy up front tells you that, you demand that they put your car back together, take it off the rack, and go somewhere else. You didn't take your car to a shop, you took it to a lie.
You're right on this. However, it's near impossible to tell up front whether the place you've taken your car is a shop or a lie, since most of them look basically the same, and you only find out after your car is in pieces up on the rack which one this particular establishment is. Which is wh
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Re:As an engineer... (Score:5, Insightful)
From my original post:
Same thing with an O2 sensor. Just because it says "O2 Sensor Three is reading incorrectly" doesn't necessarily mean the O2 Sensor is bad. You could have bad wiring, the air/fuel mixture could be throwing off the reading, the person could have just put bad gas in it, or again many other possibilities.
Have a nice day!
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I'm not a mechanic now, but I have worked at an auto shop. I don't think it's any different now with modern technology than how it's ever been. Good mechanics use all the tools at hand to find out what's really wrong, and then fix it. Crappy mechanics replace whatever part the flowchart, manual, or computer says is wrong and hope for the best. Computers only help both types do what they were already doing.
Of course the trouble is that most shops that I am aware of pay their mechanics based on fixing specifi
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That's a flawed payment structure then...
Most mechanics i know here are paid an hourly rate for their labor, they don't even screw you on parts and will quite happily let you source the parts yourself if you think you can get a better deal.
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We used to get a commission based on total parts and labor for the work ticket. One would think this would encourage us to be parts swappers and not actual mechanics, since parts make up more of the cost of a total ticket...and normally, I would agree with them. However, the culture of the shop I worked at was such that people who had a higher labor-to-parts ratio generally earned more, because they were granted higher commissions on labor, thus raising their base pay. The owners understood that not on
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Thus speaks an HONEST mechanic that I'd probably take my vehicle to. Shame you're hurt like you are- there's entirely too many people out there that're like the lie than the good shop. Seriously.
I take vehicles in, not because I don't know anything- I'm time constrained because I've other things
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> Speaking as a former mechanic, fuck you very much.
I'm glad you were a good mechanic, but this is one of those cases where "it's just the 99% that makes the other 1% look bad." Everyone knows that finding a good mechanic is like finding a needle in a haystack--it's been a cliché for decades and it's totally true. I just spent several hundred dollars across two visits to find out why the "check engine" light was on.
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As a DIY mechanic, I agree 100%. The last 9 times out of 10 I've got a trouble code via ODB-II it has been completely wrong.
When I finally learned to ignore the code and diagnose the engine I got far better at fixing the car on the first try. The onboard computer makes a guess based on the data its being fed. The problem is usually that the data is freaking wrong, which is whats causing the
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Reminds me of a problem my son had with his VW Jeta (turbo).
He complained that there was a noticeable miss-fire under hard acceleration.
Took it to the VW shop. They plugged in their computer analyzer and pronounced no problem.
He eventually persuaded the tech to get in the car took him out on the highway and floored it - misfire.
Back to the shop, plug in the analyzer - no reported misfire.
Basically, they told him to get lost. Especially since this was under warranty and if the VW computer showed no issue, th
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Many dealerships do this, but real shops do not.
and
If you go somewhere in which the guy up front tells you that, you demand that they put your car back together, take it off the rack, and go somewhere else. You didn't take your car to a shop, you took it to a lie.
Ah. 'The no true scotsman fallacy'. OP was specifically addressing dealerships if you look at it again. The attitude above bugs the hell out of me. I agree with you that it's not as simple as reading the codes and a lot of critical thinking is needed to accurately diagnose the problem. I just maintain that the mechanics' horseshit has reached the point where I'd trust a lawyer before I trust a fucking mechanic to be honest with me. Fucking crooks the lot of them and the honest ones are usually just hones
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I just maintain that the mechanics' horseshit has reached the point where I'd trust a lawyer before I trust a fucking mechanic to be honest with me. Fucking crooks the lot of them and the honest ones are usually just honest 'with people they know'. They make up their margins with customers off the street.
Sadly, I must agree with you. The shop I worked in prided itself in being honest with its customers (the first time a manager caught a mechanic trying to cheat a customer, they were fired on the spot. No second chances.) Despite our reputation and huge numbers of loyal customers, it was always very difficult to get new customers to trust us for the very reasons you outlined.
The point, as always, is that service departments in dealerships (and other shops as well) need to be hella regulated by at least 3 different agencies, with monthly audits, starting with the assumption that every single one is a den of thieves. Douchenozzles. Now, they don't even let you into the work area anymore (unless they "know" you) using some convenient OSHA rule and insurance crap and concerns for your "safety", unless you insist and threaten to take your car elsewhere.
This was something else we prided ourselves on. It's your car we were working on, and as such you had every right to see the proble
Re:As an engineer... (Score:5, Insightful)
You're both wrong.
I'm a former mechanic because 5 years ago, I fractured my left and right ulna, as well as navicular fractures in both wrists. If you can tell me how to work on cars with injuries that won't fully heal for years in both wrists, I'll be glad to do it.
To the AC, I didn't want cars returned to me, which is why I always fixed what was wrong and not what I was told was wrong by a computer.
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Sorry to hear you've lost your livelihood for some time to come.
However, you're not the norm. You're the exception to things, sadly.
A disturbing number of the people out there in the shops are "ASE certified" techs that just do things as indicated by those expensive OBDII boxes, never once thinking that it might just be a bad sensor or an unrelated cause that triggered the MIL failure. They don't stop to think what might be wrong- they just go off of what they were told by the computer, blindly trusting i
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So as a doctor do you: (A) bust someone's chops when a patient mentions something like "hitting their funny bone" or some other non "technical speak" or (B) do you figure out that your dealing with a person who isn't supposed to have a technical knowledge of the human body and actually help them.
If your answer is A you shouldn't be practicing medicine with direct contact with patie
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Maybe that's why you are a former mechanic. A good mechanic knows that 90% of the time on a specific car that a misfire on cylinder 3 is that leaking head gasket you have either fixed 50 times or read about in the TSB. Shitty mechanics are shitty mechanics with or without a scanner.
Did you actually read the GP's post?
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Re:As an engineer... (Score:5, Informative)
And the real reason the Mechanics hate doing warranty work is because the dealership screws them over too. They get paid by the job based on the complexity, and the dealership considers the same job covered under warranty to be worth about half as much. I've got several friends who make their living as auto mechanics.
It's not different to the sales department who make their money only on commission as a percentage of the profits over invoice, so to screw over the sales people the dealership sell at barely above invoice and make their money on the financing/extended warranty/accessories/etc. I've got several relatives who make their living as auto salesmen.
Dealerships will stop being scummy when they stop treating their employees like starving dogs.
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That's all well and dandy except that the scan equipment isn't actually expensive, the OP is simply looking in the wrong places.
Well, I'm not a mechanic but I do like to have some idea what's going on under the hood. I have an Android phone with a bluetooth multiprotocol OBD2 interface, and I use a program (it's in the Market) called "Torque". Works very well, and does more than those handheld scanners you buy at Sears. Even allows you to log OBD info with GPS tagging, and export it. If it finds a trouble code, it will link you to a Web site that lists the possible causes for that code for many different vehicles.
It only cost two
Re:As an engineer... (Score:5, Informative)
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Absolutely nothing... there's a reason equipment that hooks into safety critical systems is so damn expensive.
http://www.scantool.net/ [scantool.net] has open source drivers to go with their cheap USB / serial auto interfaces.
The protocol allows you to distinguish between read-only and read-write commands. I guess it's similar to using SNMP.
Of course, your safety is never guaranteed. I don't think you should take any risks today. Stay at home with the shutters drawn.
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Re:As an engineer... (Score:4, Insightful)
That said, the foregoing does not mean it's a good idea for the casual mechanic to diddle with his car's computer, in part because it was probably optimized in interdependent ways that he has no chance of figuring out, because they only made sense serendipitously when being coded.
Re:As an engineer... (Score:5, Informative)
If you're really all that concerned about making really STUPID mistakes it why not only tap into the outbound serial pin and then throw an opto-isolator on it. then you can do whatever the hell you want and not worry about damaging your engine computer.
to the OP... there are DOZENS of OBDII to Serial port adapters on eBay that sell for ~$30, I own several. You'd be hard pressed to build your own for cheaper, the hardware alone will likely cost you that much. There are dozens of free and or cheap (freediag. If you'd rather write your own SAE and ISO control the OBDII standard [wikipedia.org].
Any engineer who is too frightened to even perform some basic research on the workings of something as simple as OBDII should be ashamed of themselves.
Re:As an engineer... (Score:5, Informative)
freediag [sourceforge.net] - Open Source for Linux
OBD-Diag [obd-diag.de] - Not open source but free
Easy OBDII [easyobdii.com] - Not open source but free (I use this most often for basic diagnostics)
You might also want to check out the MP3Car forums [mp3car.com] as they're very knowledgeable on this subject over there, and there are also several source available projects being developed there as well.
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http://www.elec-intro.com/obd-schematic [elec-intro.com] schematic for ODBII to RS232. You can pick from a MAX232-based solution or an op-amp based approach. Use a solderless breadboard if you're not good at soldering or to test the circuit first to make sure it'll work for your car.
http://prj.perquin.com/obdii/ [perquin.com] another ODBII to RS232 using just a few transistors.
For a slightly safer approach using optoisolators, try http://www.planetfall.com/cms/content/opendiag-obd-ii-schematics-pcb-layout [planetfall.com]
With freediag, you should be g
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Unless you have the parts laying around already, by the time you get the parts, housing and chips needed you've already spent more than buying a premade ELM327 based scanner from someplace.
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OK, so now it's time to earn your +2 Insightful: what is the reason?
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The r
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Re:As an engineer... (Score:4, Insightful)
Re:As an engineer... (Score:5, Insightful)
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Why don't you get rid of your current car and buy a vehicle which is old enough to be (mostly) free of microelectronics?
Easier said than done, sir. Even my '79 aircooled VW bus had a computer in it. Cars that old were much more prone to rust than current ones. The government was recently paying cash for those clunkers. They're getting rare. Not impossible, but not as easy as you make it sound to buy an old car in any kind of good shape. And not cheap if you find one in seriously good condition.
Re: (Score:3, Interesting)
Probably a solid state analog fuel/ignition 'controller', not really a computer in the modern sense. I guess it's a gasser thing. An '81 Jeep I used to own had one, but the '84 MB diesel I have now has no 'black boxes' at all. You can disconnect the battery after it's running if you want.
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Why don't you get rid of your current car and buy a vehicle which is old enough to be (mostly) free of microelectronics?
Sure, go ahead and get a gas hog rust bucket with crappy emissions.
Just buy a new car. Maintenance free so you dont have to tinker. Put that spare time to something useful. My last three cars (including a hybrid SUV now) I've never even opened the hood. Couldn't care less. I put gas in and it takes me where I want to go. Every few months or so I take it for a checkup. I'm an engineer and naturally curiuis, but car engines? - I could give a rat's ass.
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For instance: obddiag.net [obddiag.net]
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Is it OBD-II? My old OBD-I vehicle did that, but I don't see how they could do it on a OBD-II car, as the codes start with a letter.