GM's ALDL info

[Oliver Scholz]

polychron at bnldag.ags.bnl.gov (Ven Polychronakos) writes:

>0A 58    00 03 53    48
>0A 58    00 03 61    3A
>0A 58    00 03 6A    31
>05 5F    00 00 00 3C 8C 39 62 01 EC 72    DA
>0A 58    00 03 69    32
>F0 55 BB

My guess would be that device code 0A is the engine RPM: in your example:

851, 865, 874 and 873.

Could you verify that?

>of data follow and ,finally, the checksum byte 48. By the way these 
>three bytes are zero when ignition is ON but engine not running.This 
Because the rpm is 0 ?

>device code seems to be repeated 3 more times in the same record!?
Because it's changing constantly ?

>The device code 05 gives 10 bytes of data from which the only one 
>I was able to figure out is the fifth one (8C= 140) which looks like 
>the battery voltage, 14.0 V, when interpreted as tens of millivolts.
Makes sense. That would be the sensory readings of A/D converters of
some kind. The leading zeroes could be non-installed sensors, unused
or reserved...

Thanks for posting that information, I think it helped a lot!
You might try disconnecting different sensors (Start with the TPS)
and see which byte becomes zero (Or $FF).
Try to force a trouble code (by disconnecting that sensor).
Maybe the last packet is not the "End of Record" (which would be useless)
but the stored trouble codes? (in your case: none) ??

Just a (more or less good) guess...

-Oliver