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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.
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
As an Engineer who owns and "tinkers" with many of my own cars I'd hardly consider OBDII a "safety critical system". in general it's designed to just be an output, it does accept inputs as well but unless you know what you're doing it's next to impossible to make detrimental changes to the programming.
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.
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.
Collector's Edition
That's all well and dandy except that the scan equipment isn't actually expensive, the OP is simply looking in the wrong places. You can order a self-contained, portable hand scanner from Jegs or Summit (without question the de-facto shade-tree-mechanic parts and tools catalogs) for about $40, you don't even need a "fancy computer" to interface with it, just the multi-meter sized device in your hand.
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.
Collector's Edition
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
I just found and bought torque the other day. Great piece of software. I've had an OBDkey for a while, and had an old palm PDA mounted in the car to run the OBD reading software. Now with Torque, I was able to ditch the palm and just use my android phone. I eventually want to play with the OBD protocol and see just what I can get my car to do or not do.