EFI guy help, or anyone else.

[Rickb1b]

So, I built this truck about 8 years ago using a 2000 explorer engine and computer. I built the wiring harness according to EFI guys plans. It’s been running great all these years. Now I’m getting a P1131 code, which says I have a problem with bank 1. So I get a better code reader and it shows no voltage on bank 1 O2 sensor, but I have voltage on bank 2 sensor 1 and 2. Now since I don’t have a bank 2 sensor 2 I can only assume I wired it up with bank 1 O2 sensor feeding Bank 2 sensor 2.

So my question is; is there any reason I would have wired it this way. It’s been a while so I don’t exactly know how or why I did what I did.

Second, looks like i need to move a wire, but i have no idea which one. Does anyone have access to the pin-out for the computer and the big square connector.

 

[73azbronco]

I would say wiring two inputs to one sensor=bad.

 

[EFI Guy]

This link will help you check your wiring. https://classicbroncos.com/forums/threads/explorer-obd2-harness-re-work.257251/post-3178461

That code does not immediately mean that the o2 sensor or wiring is bad. It just means that the o2 sensor is not switching past the .5 volt threshold.
If you have a condition that is causing that bank to be extremely lean that would also explain it. Could be a misfire or stuck closed injector, vacuum leak etc...
But checking your wiring first is free and it sounds questionable. Also inspect the wiring from the sensor back to the harness. Burning the wires on the exhaust happens to more people than it should.

 

[Rickb1b]

This link will help you check your wiring. https://classicbroncos.com/forums/threads/explorer-obd2-harness-re-work.257251/post-3178461

That code does not immediately mean that the o2 sensor or wiring is bad. It just means that the o2 sensor is not switching past the .5 volt threshold.
If you have a condition that is causing that bank to be extremely lean that would also explain it. Could be a misfire or stuck closed injector, vacuum leak etc...
But checking your wiring first is free and it sounds questionable. Also inspect the wiring from the sensor back to the harness. Burning the wires on the exhaust happens to more people than it should.

Thanks, I’ll look into all these things. The main reason I’m leaning towards wiring is because my code reader is showing a voltage on bank 2 sensor 2, but I don’t even have a bank 2 sensor 2.