I am pulling my hair out trying to obtain live data from my stock, carbureted '84 Z28 with ECM 1226455. . I am using DSD Tech USB to TTL Serial Adapter, pin D with WinALDL and cannot establish communication. Tried 10K resistor which appeared to get some communication that was visible from the serial adapter. Tried 4800 baud settings, and cycled through all the ECM's. Everything I found regarding this seems to be outdated and links that are now gone. I'm assuming I should see something in WinALDl, but maybe not? Any help would be appreciated. Thank you!

 

Pin D? I thought data comes through Pin E??? Is TXD and RXD tied together going to pin E and Ground to Pin A? I believe for the CCC ECMs, you need the 10k resistor across Pins A and B. Be advised this puts the ECM in some sort of diagnostic mode in which it adds timing, fuel and rpms which may give you data that's of no use.

 

Pin is E is blank on my connector so pin D is data from what I've found. Putting a 10k resistor in makes the engine light come on dim and lots of clicking/buzzing.

 

You're right that it is pin D. Maybe this might shed some light on additional resistors that maybe required. You gotta scroll all the way down to the last post as the pics lost their hosting... http://www.montecarloss.com/communit...&Number=998840

 

Thank you! What was described as being 12V makes sense. It also aligns with WinALDL's serial cable schematic needing a 1.5k resistor, R4, for Carb vehicles. I'll try and update my results.

 

It works! The voltage divider was it. I'll update with details soon.

 

Link to the schematic

 

Thanks for the link, you made my day.


 

added the schematic picture

 

If someone is interested in the complete cable assy premade let me know. Thanks