My newly purchased ca18det (auto) is having a wiring problem preventing startup and I'm in the process of checking the wiring harness (since I don't know the origin and if it was rebuilt). My question is, though, is it okay that my ECU plug is missing the following connections: 33 (Diagnostic Computer Connector), 47 (Diagnostic Computer Connector), 56 (Auto Trans Control), and 111 (Fuel Pressure Regulator).

The 33 and 47 make sense, but since I'm new to this engine and ECU wiring in general I figured I'd ask if the wires are supposed to be there. None of the diagrams I've found mention "optional" wires. I don't want something to fry again when I replace the shorted ignition coil, spark plugs, and ECU repair.

Thanks!

33 and 47 have no effect on the driveability of the vehicle. Without then connected, your OBD port doesn't work. S13's have OBD1, so unless you go to a Nissan dealer, the port won't do you any good anyway, so it's not something we ever worry about.

56 seems important, from my quick look at the FSM, I'm not sure of it's purpose, but it is a signal wire between the ECU and the TCU.

111 doesn't matter. It's a silly little thing Nissan do to reference the FPR to atmosphere during startup to help clear hot fuel out of the fuel rail at startup. Without it, you may have to crank the engine over a second or two longer if the engine is heat soaked. Most people don't even notice it's absence.

Thank you very much for your response!

Alright, I'll look into 56 a bit more then. If I can't find anything I'll probably wind up yolo'ing and hoping nothing blows.

Thanks, again!

If you are missing #56, wouldn't that make the ECU one for a manual?