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