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Any Open Source Solutions For DIY Auto Diagnostics?
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?"
Mixing high tech electronics with automotives has always struck me as the worst fusion of the old joke: "the difference between a computer salesman and a used car salesman is the used car salesman knows when he's lying". As an engineer it may seem like a good idea to you that the equipment is expensive, but how many mechanics are also engineers? Mechanics are often not even mechanics any more. They plug in the diagnostic and whatever it says is wrong, is what is wrong. Don't try and tell them that it doesn't make sense that a stretched timing belt is causing the shimmy coming from the front passenger wheel, darn it, that's what the computer says.
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.
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.
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.
Living With a Nerd
Translation of GP: You're not smart enough to bother looking at this, it's way too complicated. And besides, I make my living working on this stuff, I wouldn't want to lose any income because you learned how to fix your own stuff!
Little girls, like butterflies, need no excuse. -- L. Long
Yeah, it still is. People have been working on, and repairing, their own safety critical equipment as long as there have been cars. Brakes are definitely safety-critical. I have done mine more than once over the years as a simple example. Just because it's safety-critical doesn't mean people can't learn how to DIY repairs, as long as the information is available. All this ODBII secrecy is just for the auto industry to extort money from the auto owners.
Little girls, like butterflies, need no excuse. -- L. Long
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.
Living With a Nerd
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!
Living With a Nerd
Currently you need a specially-adapted laptop, a highly proprietary cable, and some very expensive software. Garages can afford this: individuals can't.
"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.