I am the original owner of a 90 RX7 GXL with 299k miles. I put in a remanufactured rotary at 211k miles. Here is my problem. My CEL has been coming on recently but car runs fine. I tried to read out the codes but there were none. I have about 60k on the O2 sensor so I thought I'd replace it. Discovered the wire from engine harness to O2 sensor is missing! I checked under the car but couldn't find any loose wire hanging. So, apparently someone cut the wire or I was torn off somehow (maybe a branch?). In any event, I'd like reconnect the O2 sensor because my gas mileage sucks. I also have VA emissions coming up in a couple months and won't pass without O2 sensor working. Can anyone with late 2nd gen tell me at what point O2 wire branches off the main harness? Please be specific. If available, a photo would be very helpful. Thanks!

Hot_Dog
90 RX7 GXL w/ 299k miles

 

I got the same problem, Cant find the o2 wire to save my life lol. looked EVERYWHERE.

 

The wire runs to pin 2C of the S5 ECU. If at worst, you could just run a new wire from this ECU pin.

 

That's exactly what I'm trying to avoid.

 

How did your wire disappear?

 

I have same issue! If someone has a write up or how to fix issue without re-wiring the ecu?

 

Running a single wire from point A to point B should be rather easy.

 

is it the same on a s4? i'm probably going to have to do the same.... :/

 

As a last resort, I will run a wire from the ECU to the O2 sensor. Accessing the ECU is and splicing in a wire may be difficult. I'm looking for a simple fix.

Does anyone have a photo showing where the O2 wire emerges from the harness? That would help me a lot!

 

Pin 2D for an S4.

 

Post #2 might help:
https://www.rx7club.com/2nd-generati...estion-991062/

 

Ok...thanks! I'll check it out this weekend.

 

Ok...I found the dangling wire, spliced in a new piece of wire and reconnected the o2 sensor. The car seems to run better and hopefully the my gas mileage will be better. Not sure how this happened, but the dangling wire looked as if it had been smashed a bit.

On the late n/a 2nd gen, the wire comes off the main engine harness which is routed behind and slightly left of the alternator. The wire runs under the TSP connector. It is a single wire and it has a plastic protector sleeve around it.