Serial data output
Thread Starter
5th Gear
Joined: Feb 2019
Posts: 5
Likes: 0
Serial data output
Trying to source a "logic module" for my 89 C4. Built and installed an analog dash panel. Problem is that I now have no "serial data out to ECM A8 and ALDL pin E. Tried to contact Vettaid, but he doesn't return calls. Also have sent an E-mail to Speedhut. So far I've been unable to find which inputs make up the "serial data" or how it is processed to convert it to "serial data out". Hopefully some in the C4 Community can offer some assistance.
Drifting
Joined: Jun 2018
Posts: 1,402
Likes: 287
From: Brisbane Australia
C4 of Year Finalist (performance mods) 2019
Trying to source a "logic module" for my 89 C4. Built and installed an analog dash panel. Problem is that I now have no "serial data out to ECM A8 and ALDL pin E. Tried to contact Vettaid, but he doesn't return calls. Also have sent an E-mail to Speedhut. So far I've been unable to find which inputs make up the "serial data" or how it is processed to convert it to "serial data out". Hopefully some in the C4 Community can offer some assistance.
Melting Slicks
Joined: Aug 2003
Posts: 3,389
Likes: 391
From: Lakeville MI
In normal mode, 5 bytes of serial data is transmitted from the ecm to the dash at 160 baud in order to activate the shift lamp, OD or Cags indicator, and provide running fuel and distance counters along with the gallons/hr display constant for the average and instantaneous mpg calculation. The dash does not transmit anything to the ecm. Nothing to worry about.
More detail below. I knew I posted on this topic somewhere before, but took me awhile to find it:
https://www.corvetteforum.com/forums...post1597768204
Vehicle speed output from the dash to the ecm (2k ppm) may be an issue, but this is a different topic entirely.
More detail below. I knew I posted on this topic somewhere before, but took me awhile to find it:
https://www.corvetteforum.com/forums...post1597768204
Vehicle speed output from the dash to the ecm (2k ppm) may be an issue, but this is a different topic entirely.
Last edited by tequilaboy; May 10, 2019 at 08:23 AM.
Thread Starter
5th Gear
Joined: Feb 2019
Posts: 5
Likes: 0
Success!! Turns out that a "logic module" was needed. The OE digital dash converts the 4K pulse VSS input to 2K for output to ECM and Cruise Control. Dakota Digital sells such a module for $84.95. Part # SG1-5E. Once mine was installed, my drivability issues immediately went away.
Melting Slicks
Joined: Nov 2007
Posts: 2,830
Likes: 147
From: Gainesville FL
Success!! Turns out that a "logic module" was needed. The OE digital dash converts the 4K pulse VSS input to 2K for output to ECM and Cruise Control. Dakota Digital sells such a module for $84.95. Part # SG1-5E. Once mine was installed, my drivability issues immediately went away.
Thread Starter
5th Gear
Joined: Feb 2019
Posts: 5
Likes: 0
Injectors did not "shut off" during "coast down" and engine would stall at stops. Engine would idle immediately when it was restarted. After installing the module, the injectors and idle control functions are as they were with the digital dash.
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