Car computer Code Reader
Clock Loop
Posts: 2,069
Has anyone here made a program, or know anything about reading the computer codes from a car?
I know the newer OBDII type connectors on all 1996 and newer models is quite complicated, but the older GM cars have ODBI type interface connector called the ALDL. DRBII
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Meh. Nothing here, move along.
Post Edited (BPM) : 1/16/2006 10:40:24 AM GMT
I know the newer OBDII type connectors on all 1996 and newer models is quite complicated, but the older GM cars have ODBI type interface connector called the ALDL. DRBII
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Meh. Nothing here, move along.
Post Edited (BPM) : 1/16/2006 10:40:24 AM GMT
Comments
For '96 and up cars, check out the ELM233 by Elm Electronics. I don't know anything about vehicles previous to that.
Jonathan
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www.madlabs.info - Home of the Hydrogen Fuel Cell Robot
http://www.jaycar.com.au
When their site is back up, they might be a good place to start.
Vern
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But, cars have at least two different communications buses - CANbus is Japanese and European and then there is an American one. They are mutually incompatible.
So, assuming that you want to interface with the 'computer' via the communication bus, you have to provide a make, model, and year of auto to identify which bus and which version [noparse][[/noparse]CANbus is up to V2.0b]. Even with that knowledge, your interface may have to be specially adaptible to 'hot-plugging' into the bus to identify the nominal baud rate.
I guess the automotive people really want to keep this in their 'voodoo department'.
Also, CANbus can easily support more than one Master Computer and numerous Slaves as each reciever filters out the messages that don't apply to it. 64 devices are easily achieved and many more could be placed on the bus if they are not too active [noparse][[/noparse]it is all about how much traffic in terms of transmited messages are going out].
CANbus seems to be moving into other fields and may even take over the American car market as it is quite robust and well documented. I have read about it being used to control automated looms in a large weaving mill. It is quite adaptible to noisy electrical environments and very appealing to industrial and home automation.
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"When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)
······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan
I was able to interface to the chip (they provide a nice big schematic to talk to the chip)...but never had the chance to plug in to the OBD2 connector in the jeep.
(I shelved it due to having to work out in the cold to do it....but this was 2 winters ago....and it's -10degC out right now and I am still keeping it shelved!)
Anyhow, you can do some nice basic stuff with the controller....but I wouldn't want to change tunings on the fly with it....just would like to monitor engine codes and temps/pressures and such!
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Steve
"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
Yea I wanted to do this also.
But the damn car companies don't wanna give up the data....
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Meh. Nothing here, move along.
I'll try and dig up what I found....but it didn't give me enough of a picture on how to do it with just a stamp.
If I recall (and that's risky!) I found a prelimary paper on what they wanted to do...but this was pre-OBD2 days and they probably changed it for the actual implementation...which is why its not public on the net!
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Steve
"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
First you need to know which SAE (Society of Automotive Engineers) OBDI specification is being used on the car in question, or whether some other protocal is being used. As I remeber, the SAE will sell you the complete specifications. It would probably cost you more for the SAE OBDI specifications than it will for the appropriate ELM (or equivalent) converter chip, to bring the signals out to you in RS-232 format. Obviously, once it's in that format, you can use darned near any computer or microcontoller to access it, and analyze it, to your heart's content.
Without using such a converter chip, it would be most difficult to utilize a PBASIC Stamp to access the native signals produced. Some are variable frequency, some are variable width, and some are both, depending on the format. You could undoubtedly utilize a Parallax SX/B or MicroChip PIC platform to analyze it, process it, or generally utilize it as you saw fit.
Considering all of the world's automobiles, as I remember, there are a total of only 4-5, possibly 6 different "formats" or protocals. Each manufacturer COULD have implemented their own proprietary protocal, with none of the overlap which presently exists. I suppose we can all be grateful that is not the case.
Regards,
Bruce Bates
······ http://casavista.calinet.com/OBDII/
It didn't give me all the info I wanted (I'm a tech...I want the guts!!)...here's a blurb from the book (paraphrasing where I'm too lazy to type it all out)...
"...OBD2 recognizes several different protocols. At this point, we only need to discuss 3 of them: J1850-VPW; J1850-PWM; and ISO9141, which directly affect all the vehicles in the US." and Canada too!
"...SAE has defined 3 distinct protocol Classes: Class A, B and C."
"...A is the slowest at a peak of 10kb/s. The ISO9141 standard uses class A."
"...B is 10times faster and supports comms as high as 100kb/s. The SAEJ1850 standard is class B."
"...C supports comms as high as 1Mb/s. the most widely used vehicle-networking standard for Class C is Controller ARea Network (CAN). Higher performance communication classifications from 1Mb/s to 10Mb/s are expected in the future. Classes like 'class D' can be expected as bandwidth and performance needs go forward. With Class C, and the futureistic Class D protocols, we will be able to use fiber optics as cabling for th enetwork."
<pants....>
"J1850 comes in 2 flavours. The first is highspeed 41.6kb/s Pulse Width Modulation. Ford, Jaguar and MAzda use this. ....uses 2 wires, pins 2 and 10 of the diag connector."
"the 2nd flavour runs at 10.4kb/s using Variable Pulse Width. Both GM and Chrysler use this protocol. Similar to PWM but slower. Uses 1 wire, pin 2 of the diag connector"
(also need a ground on these....)
"ISO9141 ismostly used by european, asian and some chrysler vehicles. ...not as complex as the J1850standards. ...uses standard off-the-shelf serial comm chips."
Not sure what else you mights want out of it....ELM does supply a chip for each of the 3 (or at least the j1850) protocols.
This book isn't bad...a bonus is that it dedicates a chapter to some Venezulan cooking. haha
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Steve
"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
http://www.techedge.com.au/vehicle/aldl8192/8192hw.htm