Retrieving ECM data with PC

[John T Stein]

I am trying to find software (PC) to read out, decommutate, and 
display data stored in a General Motors engine control computer.  
Does anyone have, or know of the existence of any such software?

Any other information about the format and organization of the 
telemetry available at the ALDL connector; e.g word sizes, baud 
rates, data order, etc. would be appreciated as well.

I would expect the ALDL data rate to be low enough to allow the data 
to be received by the PC serial data port.  I would also expect that 
the only hardware needed would be a line receiver for the ALDL data 
and a suitable driver to sink the ALDL test pin to ground.  Are these 
assumptions valid?

I am sure this has all been done by someone already, does anyone 
out there have any experience they could share with me?

Thanks, 

John