Serial Data Input?
Thread Starter
Burning Brakes
Joined: Jun 2005
Posts: 1,188
Likes: 13
From: Wallingford Vermont
Serial Data Input?
I'm attempting to convert my '86 from the "Atari" digital dash to analog gauges ('89 Firebird). I've got a 4 Out Speed Buffer, a Cruise Control Module, and a nice Racetonix header plug to connect the factory harness. I've identified all my connections except one. The "Serial Data Output" that comes from the OE instrument panel (connection D10 to circuit 461) then connects to the ALCL (terminal E) and the ECM (connection A8).
Now the FSM shows this as an output from the panel and a input to the ECM. This seems a little backwards to me, but I don't know the purpose of this connection. What is it? Does the ECM need it to operate?
Now the FSM shows this as an output from the panel and a input to the ECM. This seems a little backwards to me, but I don't know the purpose of this connection. What is it? Does the ECM need it to operate?
Safety Car
Joined: Jan 2004
Posts: 3,556
Likes: 13
Thread Starter
Burning Brakes
Joined: Jun 2005
Posts: 1,188
Likes: 13
From: Wallingford Vermont
Well it's still a '165 MAF ECM. But why would the FSM show this as an "output to the ECM" (in a couple of diagrams)? The actual VSS signal goes straight to the gauge panel (C15, D11). The FSM cluster connection diagram also indicates the output as "toggling 2 to 4 volts" FWIW.
Other '165 diagrams (like the Firebird) only show this as a ALDL connection only. So I'll assume the FSM got it wrong and it is an output from the ECM to the cluster panel (for mileage, etc.)
http://www.chevythunder.com/fuel%20i...%20#1227165%29
