A great freeware PC scan tool is now available and obsoletes the software available here.
http://w1.601.telia.com/~u60113744/software/winaldl/winaldl.htm
Back in '97 I was unable to find any free scan tool so I whipped up a nasty basic program to decode
the datastream using brute force. Not much has really happened since then but I keep the page here to assist
people looking for information.
My car is (was :) a 1986 Buick Skylark with the GM C3 ECM.
I also have some DIY_EFI archive info the 8192 bps (P4?)
ECM right here.
The above picture depicts a snapshot of data from the ALDL connector. The top purple trace is on a 5 milisecond grid. The bottom green trace is shown 2x faster, at a 10 msec grid. The bits are 6.25 miliseconds apart. A falling edge marks the start of a bit. For the puprle trace, the first bits are 0's, and the last bits are 1's.
Dead links you might want to track down: ni.umd.edu/gnttype/www/ecmpins.html ECM Pinout Map www.geocities.com/MotorCity/Speedway/5036/ecm-codes.html Another ECM Trouble Codes & ALDL Pinout ni.umd.edu/gnttype/www/malf.html ECM Trouble Codes & ALDL Pinout www.access.digex.net/~miked/codes.html Monte List: ECM code reading www.telepath.com/dbyrer/aldl.html ALDL Pinout efi332.eng.ohio-state.edu/diy_efi/ Do-It-Yourself Electronic Fuel Injection Mailing List www.franken.de/users/dagobah/luke/scantool.html Oliver Scholz Scantool Home Page