Talking to my PCM!

[David A. Cooley]

Hello all,
I'm Talking with my PCM in my 95 Buick LeSabre now...
It appears the 95 ALDL datastream is standard ALDL.


1 byte device code
1 byte: 85+N (N being the length of the data part of the packet)
N data bytes
1 byte checksum

Except for data from the ABS... the format is identical but there is no
checksum.

The device codes are:

20
90  
91 ABS
A1 (Air bag module)
A0 (Trouble codes)
A8
F0


I isolated the ABS and Airbag modules by disconnecting them...  A0 was always
sending A0 55 0B  which was 0 databytes and a checksum... until I set a code!
90 appears to be RPM...  With the engine off, it's sending:
90 59 00 01 00 5C BA
Running (At idle) it's:
90 59 20 01 07 5C 93
Not sure what the 5C is or how to calculate the RPM from the 3 bytes...

20 has a lot of codes associated with it... it's data length is 7... an
example
line just after start-up:
20 5C AA 09 00 7B 00 00 6B EB

And after about 10 minutes of idling:
20 5C AA 09 00 8B 00 00 68 DE

A8 is always A8 56 44 BE
and F0 is always F0 56 F4 C6


Haven't tried driving yet...

Anyway, this will help with the disassembly of the code in the prom as I now
have addresses being sent out (device codes) to compare with the code.

Thanks,
Dave

===========================================================
           David Cooley N5XMT           Internet: N5XMT at bellsouth.net
     Packet: N5XMT at KQ4LO.#INT.NC.USA.NA   T.A.P.R. Member #7068
                     We are Borg... Prepare to be assimilated!
===========================================================