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Connecting To An Automotive Diagnostic Computer?
An Anonymous Coward writes: "I was wondering if anyone has tried to hook up a PC to the diagnostic computer on an automobile. Each time the little idiot light on my Blazer comes on I have to cough up $20 - $40 just to find out what the problem is. This seems to me like an amusing and only moderately difficult hack - I can't believe that I am the first person to think of it. However, I can't seem to find any information on the topic at all."
Up, Up, Down, Down, Left, Right, Left, Right, Gas, Brake, Start gave me infinite Gas.
Here is a link to anECM scanner (a device that will read the diagnostic codes on modern cars) for only about $500. It looks like it can handle a wide variety of Chrysler, Ford and GM vehicles built between 1984 and 1995.
The company sells a few other interesting toys that could be of use to automotive/electronics geeks.
Otherwise, there are some links I found along the way:- Miata Engine Computer Self Diagnotics
- Chrysler, Plymouth, and Dodge Computer Fault Codes
- Datalogger a commercial hack from TechnMotive similar to the poster's requrest. There may be other good stuff on the TechnoMotive site.
- An overview of electronic engine control from Intel.
I got these links simply by doing a Google search on "engine computer diagnostic". There were many more (about 4000 pages worth) but I got tired of skimming through them (I was averaging about 2 usefull hits per page).See also www.obd-2.com (if your time has no value and/or you just want to tinker).
For that matter, I had difficulty a couple of years ago when an alternator failed and the idiot light wasn't visible through my sunglasses...
Quite some time ago I was searching around the net for exactly the same thing, just out of curiosity. Unfortunately I didn't keep any of my bookmarks on this (and they've probably 404'd anyways), but many manufacturers encode the error "codes" as a series of pulses. Using a multi-meter or a simple 12V bulb, you can count them and get the error code. They're not even encoded in any way (BCD or whatever), but rather the number of pulses is directly equal to the code. Building a simple circuit to record the error codes and later dump them in a serial port (or parallel if that's your thing) shouldn't be too difficult.
A Google search turned up some examples of codes, so they're out there; you just have to look!
Ford Probe
Eagle Talon
Most of the better shop manuals you can buy also have most of these codes. Take a look through some of the aftermarket books like those from Haynes or Chiltons or whatever you can find.
It's only software!
If you have a Holden VN,VP,VR or VS this might be of interest to you.
that's funny cause my car accelerates when I push down on the accelerator too! :-)
Anyway, it may not be a trivial hack. I suggest that you think about asking your car mechanic (You are friendly with him, aren't you? If not, ask another shop.) if there are any specs in the repair manuals, or if he can share anything with you. He may get nervous (NDAs for diagnostic operators), or mislead you (he'll make less money if you succeed), so be careful about who you ask and how you ask.
And if you have any success, please share it. I can imagine a convergence of car guys and computer guys working on their cars, crossing social boundaries, living in harmony with each other and nature, learning from each other, ... uh, whoops. How did I have a flash-back to the 60's when I was born in the 70's?
Good luck with your car.
Louis Wu
"Where do you want to go ...
Alright, the first thing you need to do is to go down to your local autozone/shucks and buy a book of your partiular model. Inside, it should tell you how to enable your code and how to decipher it. For example, I have a 95 dodge neon, and the procedure goes like this:
OBD stands for On Board Diagnostics, and is a federally mandated specification for new cars, largely aimed at reducing emissions. The car logs certain problems that occur, and activates the 'Check Engine' light (CEL) to alert the driver. A mechanic with the proper DRB Scan Tool can the review this log in some detail to assist in repairing the problem. The most direct benefit is that owners can access some of this information themselves. Certain codes will set off the CEL while driving; some do not. It is a good idea to check for hidden codes occaisionally.
To read any OBD codes, perform the following sequence.
1) Cycle the ignition key ON-OFF-ON-OFF-ON within 5 seconds.
2) Count the number of times the 'Check Engine' lamp on the instrument panel flashes on and off. The number of flashes represents the code. There is a slight pause between the flashes representing the first and second digits of the code. Longer pauses separate individual codes. For example, flash-flash-flash [pause] flash-flash represents the code 32.
You should have a similar sounding thing in your book. Most of the time the problem with the "service" light means that you need to fix somthing electrical (usually a 4-5$ part and fixable yourself, the guy at the auto parts store can usually tell you how to install it for free) or your timing is off for whatever reason.
My dad has had caddies since the late 70's, and the ODB readings were accessable through his electronic climate control by pressing and holding certian buttons, but good luck finding a book on caddies with that kind of information, caddy ODB numbers are only listed in special dealer "how to fix everythig" books from the GM press that we managed to find at a swap meet in seattle on weekend.
where i got the info on the neon was at http://www.neons.org/faq/FAQ_ET.html
moox. for a new generation.
First oof, I need more information to be able to help you out. What year is your Blazer? This is the most important piece of information. If it is older than 1995 then you can do it yourself with a paperclip. However, if it is newer than 1995 you're out of luck. The only way to get those codes is to let an automotive technician look at it. If it is older than 1995 take a paperclip and bend it into a U shape. With the ignition turned of, place the paperclip into the upper right two oenings in the diagnostic connector (ALDL), located under the dash. Turn the key on and watch the engine light. Count the number of time that it flashes. It will repeat each code three times. The first one should be a twelve. This means that the computers diagnostic circuitry is ok. It is represented like this: flash pause flash flash long pause flash pause flash flash long pause flash pause flash flash. If there are any other diagnostic codes they will flash after this one, otherwise code twelve will flash repeatedly. Go down to your local library or Autozone. They usually have Chilton's manuals that include the defenition of the codes. In fact Autozone should be able to print up a list of the codes for your specific vehicle form their computer system, free fo charge. Good luck.
This guy has incredible "true" hacking skills. Whether it's cars, arcade boards, even designing a user-friendly gameboy cartridge reader... unfortunately, not all of his site is in English, and I think he only has hacks for cars he owns... He might be able to provide some good starting info though...
I use stuff like this all the time. I often have my problems diagnosed before I drive into the dealer. I have a Volkswagen and use the Ross-tech VAG-COM. The now defunct CarComp also had a great tool available for similar purposes. Conveniently, the hardware interface also works for my Dodge truck with different software.
This guy seems to have what the poster is looking for. He covers building your own tools for GM cars.
I saw some devices mentioned above that do this job (and probably alot more judging from the pricetags), but if you want just a device that spits out the code, this would be your thing. Usually they come with a book/papers that tell you what each code means (lean oxygen sensor, bad fuel sylenoid, etc). This box, roughly the size of a TI graphing calculator (but not nearly as good a display, if one at all) has a cable interface/wires coming off it that you hook into the computer system. I know on my dad's Oldmobile station wagon (ha!) you plugged into the computer through a wire harness in the glove compartment. On my Ford Tempo I believe you hook up through a wire harness that is under the hood. So it'll vary, but should be easy enough to find, heck the book that comes with the decoder device will probably give you an idea of where it plugs in.
I tried to find a link to one on the web, but could not unfortunately. However I know Wal-Mart, Napa Auto Parts, Autozone, and several other auto parts dealers carry these devices. I'm sure if you looked around or asked someone in their store they would know what your talking about. I know one in particular that works on both GM and Ford cars. They cost about $25-$40 depending on the brand and probably some of the bells and whistles.
If you already have a multimeter and can get the probes onto the right pins to get the code, I would say just go that route.
Bruce
I have a friend who works on diesel trucks. He once showed me exactly what the diagnostic computer can do. This computer could change the idle level of the engine, it could even accelerate the engine as if someone was pushing down on the gas pedal. One thing that was a little scary is that computer kept a log of how the truck was driven (idle time, shifting habits, speeds, etc.)
So, you want to talk to your car's computer? OBD II is the standard protocol (On Board Diagnostics v2). As of about 1996, most all cars use this protocol, and also have the standard OBD II connector and hardware interface. Typically the connector will be inside the car, under the dash or behind the ashtray, someplace like that. The device your mechanic will plug into it is called a "Scantool". Some manufacturers of these include Actron and Snap-On.
The standards are documented in SAE (Society of Automotive Engineers, http://www.sae.org/) publications SAE J1978 (OBD II Scan Tool) and J2201 (OBD II Scan Tool Universal Interface) and a slew of supporting documents. I see on their website they are selling a book with a collection of these ("SAE On-Board Diagnostics for Light and Medium Duty Vehicles Standards Manual") They are not trivial to interface to.
Prior to OBD II, there was a multitude of "standards" and you had to get a different scantool, or a different interface module, to deal with each of them. Each vehicle manufacturer rolled his own. And of course, back in the dark ages, primitive on-board computers would blink dashboard lights and stuff like that to read out codes. ("Codes" in this context stands for "Engine fault codes" that describe specific failure conditions.)
It's amazing what data you can get with OBD II: current RPM, speed, status of various systems, temperatures, pressures, flow rates, and voltages in various parts of the engine and drivetrain. Have fun, I hope you're able to get something going.
-Th
http://www.autotap.com/