d.fens
+1y
Most FI systems compare inputs from the vehicle speed, engine speed, and / or throttle position sensors to calculate the timing map(s).
Fuel control is 02 sensor, manifold pressure or mass air meter, and throttle position. The coolant temp sensor turns the 02 control on (closed loop). Cold start, idle and full throttle are open loop (no 02 control).
You also lose 02 sensor function if there's an emissions-related fault in the system - CTS, 02, EGR solenoid.
I'm still learning about this GM EFI shit, but on paper it looks similar to Volkswagen's Digifant I system.