kerr@tron.UUCP (Dave Kerr) (08/07/90)
I'm posting for a friend who doesn't have access to the net.
Please reply to him directly at the following address(es).
Thanks in advance,
Tom Diviney
Westinghouse Electric Corp.
PO. Box 746, MS. 60
Baltimore, MD 21203
(301)765-4453, (WIN) 285-4453
VAX-mail: diviney%eclus.dnet@tron.bwi.wec.com
Unix-mail: diviney@sky00.bwi.wec.com
--
I would like to find information on the technical details of the
diagnostic serial data link used by all the major auto manufacturers. I have
experimented with this "Scan" link in my 1988 Olds Calais, and discovered that
it uses a standard serial format (1-start, 8-data, and 1-stop bit). The logic
levels are TTL (0-5V), and the baud rate is around 8000. The data is send in
25 character bursts spaced every 200 mS. The service manual lists about 23
parameters which can be read by a "Scan tool". I can read the raw hexadecimal
numbers, but I would like to know how to interpret them. Does anyone know
where I can obtain the following information:
1. How are these 25 bytes of information mapped into the
measured parameters?
2. What are the conversion factors (ie. volts per quanta etc.) ?
3. Is this a standard format for all GM cars with ECM's ?
(Other Olds models in my manual seemed to have a different
list of parameters than mine).
4. Is this a standard for all american cars (Ford, Chrysler, and GM) ?
5. If not standardized, what are the formats for the other
manufacturers?
P.S.- Sears does sell a "Scan Tool", but the cost is around $370
plus $130 for each ROM (unique to each auto manufacturer).
I am convinced than a simple PC program can do the job of
the "Scan Tool" without the $500 price tag.
Thank you for any related information.
--
--
Dave Kerr (301) 765-4453 (WIN)765-4453
tron::kerr Internal WEC vax mail
kerr@tron.bwi.wec.com from an Internet site
kerr@tron.UUCP from a smart uucp mailer