PC Scan Tool

(Nov 2010, FYI This page is quite obsolete and links are not being maintained. For some reason it's still popular. Maybe it's taking search hits it doesn't deserve or it's still of use. If you have any useful feedback let me know and I will add it.)

A great freeware PC scan tool is now available and obsoletes the software available here: http://winaldl.joby.se/

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.

ALDL Serial Data Waveforms

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.

Interface Info:

ECM Serial Data Protocol
What all the numbers mean
C++ Scantool. Abandoned.
BASIC Scantool. (Software to read ALDL data from a Parallel Port, Nasty coding.)
Car to PC Interface details
What the bytes mean on my Car
Daniel Burk's 1985-1986 ALDL information for GM 5.0 & 5.7L TPI applications

Daniel Burk's 1985-1986 ALDL information for GM 5.0 & 5.7L TPI applications (Local Copy 1998)
Dan's ALDL Information Page (Local Copy 1998)

ECM Trouble Codes & ALDL Pinout (local Copy)
GM ECM Trouble Codes (local copy)
Resistor Values for Diagnostic Modes


Dan's ALDL Information Page [Read this Page!]
A Car to PC Interface that might work with the commercial Diacom software.
Implementing the J1850 Protocol
AutoDOC, a free implementation of an OBD-II capable scantool.
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

Parallel Port Information

Directory of /pub/user/rstevew/LPT
Parallel Port Central
IBM Parallel Port FAQ/Tutorial Version 0.96

Click here to send Email
Copyright © 1997, 1998, 1999, 2010 Seanster. All Rights Reserved.