Lambda Sensor Wiring

[PaulRandall]

I'm restoring a 1980 Fiat 2000 that I did not disassemble. So it's hard to figure many things out.

On the passenger side of the engine, the round black wire connector from the lambda sensor fits nicely into the round connector with a green wire coming through the firewall from the electronic control unit. Also, a large black wire comes through the firewall from the electronic control unit which I can't figure out where it goes. its connector has both male and female options.

If you look at the wiring diagram for Fuel Injection System Circuits, there are 2 dashed lines surrounding the wire from the lambda sensor.

1. Does anyone know what the dashed lines mean?

If you follow the wire from the lambda sensor to the electronic control unit it appears to possibly make 2 connections to the electronic control unit. They are marked 23 and 24. Does this mean that the lambda sensor connects to 2 wires of the electronic control unit?

2. Does anyone know if the wire from the lambda sensor is supposed to connect to the green wire and the large black wire from the electronic control unit?

Thanks,
Paul

[18Fiatsandcounting]

Paul, I think I can answer most of your questions. I'm guessing that you have a California car as FI wasn't introduced into the other states until 1981. At any rate:

1. Dashed lines around a wire usually mean that this wire has a shield around it, most often grounded but not always. The central green wire from the oxygen sensor connects to terminal 24 of the ECU, while the shield for this wire connects to terminal 23 (using a white wire near the ECU I believe).

2. The wire from the oxygen sensor itself (usually black) connects only to the green wire. The shielding for the green wire (as described above) is probably necessary because the oxygen sensor generates low voltages with a high impedance circuit, and extraneous electrical noise would interfere with its signal. Lightning might even affect it if it weren't shielded. The other connection for the oxygen sensor is the ground of the engine itself, in this case the exhaust manifold.

-Bryan

[PaulRandall]

Bryan,

Thank you for your reply. It makes sense now and I've got it all wired up. (In the engine bay)

Now comes connecting all the wires under the dash! We'll see how that goes.

Paul