Wow. Great discussion on this. Thought I would add in some missing bits about the other parts of those big comma separated strings you find in the shop manuals. This is from what the 95 Mustang shop manual says
The entire string of digits is a way of telling your scan tool how to run the operation and interpreter the result it gets back for you in a nice textual format. The string is contains seven fields separated by commas. They are
1 - string id number (any two hex digits)
2 - total digit of string count (including the commas)
3 - transmit type
4 - transmit field (you guys were right in picking this out)
5 - receive filter field (may be blank)
6 - receive data processing field (commands the scan tool interprets to clear the screen, position the cursor, ASCII code to display in text, provide spacing, data conversion, byte number containing information, and code for altering execution)
7 - data security verification (total hex ASCII value of characters in the string)
So, in short, the only thing you have to transmit is (4). Looking at the ASCII version of (6) will give you some hints as to what a tool that supports these codes could display based on the results. For example, from the earlier
08,3E,22,C4103382,,9E00445443287329208042208062208082A851FF,34
08 - identifier
3E - 62 characters in the above string
22 - transmit type 22 (whatever that means)
C4103382 - what to send
- no filter on results
9E00445443287329208042208062208082A851FF - instructions to the tool on how to turn the results into something nice for the user to see (putting this through a hex -> ASCII converter shows that it contains the string DTC(s))
34 - a checksum so the tool can verify that the user entered the string correctly
Finally, I would note that this is all apparently part of the short lived Expanded Diagnostic Protocol (EDP). The full details are in J2205 if you can locate a copy (I haven't been able to) or are willing to fork over 78USD to buy it from SAE.
Cheers! -Tyson
