There is some interest in Mode 6 because the information it provides can sometimes give "early warning" of problems, and also because it tends to be poorly documented (unless you pay for access to the information). Here's what I've been able to piece together from looking at the code. Although I prefer not to post before I think I fully understand a mode, in this case I decided to just write up what I've found so far, because it may be a while before I figure it out completely. Until then, perhaps this partial explanation may prove useful to someone.
Mode 6 supports the following TIDs (the request should only be the mode and the TID, with no other data bytes, which means a total request length of 6 bytes when you include the header and checksum byte):
00 - TIDs supported 01-20 (they are: 01, 02, 03, 04, 05, 06, 11, and 20)
20 - TIDs supported 21-40 (they are: 21, 22, 31, 32, and 40)
40 - TIDs supported 41-60 (only 41)
01 - for component ID (CID) 11, the test value stored at 10F56 needs to be less than 422
02 - for CID 11, the test value stored at 10D46 needs to be less than 62
03 - for CID 11, the test value stored at 10D4A needs to be less than 50
04 - for CIDs 01 and 02, the test value stored at 10970 needs to be greater than zero
05 - for CID 01, the test value stored at 10972 needs to be greater than zero
06 - for CID 01, the test value stored at 10974 needs to be greater than zero
11 - for CID 11, the test value stored at 10F5A needs to be greater than 40
21 - for CID 00, the test value stored at 10F6A needs to be less than the limit value stored at 10F6E
22 - for CID 00, the test value stored at 10F6C needs to be less than the limit value stored at 10F70
31 - for CID 00, the test value stored at 10F72 needs to be less than the limit value stored at 10F74
32 - for CID 00, the test value stored at 10F76 needs to be greater than the limit value stored at 10978
41 - for CID 00, the test value stored at 10F5C needs to be less than the limit value stored at 10F5E and greater than the limit store at 10F60
I got a little help by comparing the format of the reply message that the code puts together to the ISO 15031-5 spec. However, I don't yet know what each test value represents. I also don't know what components CIDs 0, 1, 2 and 11 refer to. I don't even know what the limit values are in some cases (although you could determine this pretty easily by simply plugging a scantool into the car and sending the appropriate Mode 6 requests). If anyone has this information and would like to share, please post a comment. I should eventually be able to figure it out on my own from looking at the code, but I would definitely appreciate it if someone could save me the time by telling me what the above tests are all about.
Next time, Mode 7, which is very similar to Mode 3.
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