For the life of me I can't figure out what's going on with my O2 sensor and my A/F gauge. I'm starting to think there's a problem in the ECU! I've connected the A/F directly to the ECU O2 sensor pinout and I get all bars lit up as the car warms up in idle and it stays there when I drive. Now today, I unplugged the lead from the O2 sensor from the connectoer and spliced the A/F wire right onto the O2 sensor and at idle I…with the O2 sensor unconnected from the ECU I get a proper reading on the gauge, when I plug the connector in I lose all readings. Is this a grounding problem with the ECU? I have to wonder if I had shorted something out on the ECU—the car's been running very rich. What would be some symptoms of a fried O2 circuit?

Is there a "fix" similar to the BAC/ECU fix? I can't read a wiring diagram very well and I'll probably short out the ECU attempting to track this down—again.

ANY input would be appreciated!

B

 

You might have a shorted out 02 sensor wire. The wire should be a shielded wire going to pim 2D at the middle plug on the ECU. The pin 2D is on the bottom row, second one from the right as you look into the ECU. Take the plug off the ECU and disconnect the wire from the 02 sensor. Ohm the pin 2D at the ECU harness to a good chassis ground. There should be no continuity. If there is look for the center conductor and the shield touching somewhere. There is a slight flaw in the above idea in that it would not explain the first part of your thread.

 

isn't it supposed to be 2C? my pinout shows O2 to be on the top row, middle, 2 from right... thats what i connected my turbo timer to, at least..

 

Muahaha! BACK FROM THE DEAD!

The problem was a short in the shielded wire on the O2 sensor. Lesson learned: Splice as close to the original sensor as possible...I blelieve there is about 6" of unshielded wire.

 

well, originally i had the timer spliced into the pin 3 from the right on top because thats where apexi told me to put it.

however the timer isn't really acting right, so this morning i doublechecked the FSM and it shows the o2 being 2 right on top.. so i moved the wire, and now my o2 level shows as .05 instead of .50 or so

A/F doesnt work yet on the timer.. just keeps blinking like its waiting for a signal from the o2 sensor..

should i be splicing into the 2nd over from the right on the bottom row if im going into the o2?

 

OOOps. 2D on a 86-88 model. 2C on a series five 91.

 

OOOps. 2D on a 86-88 model. 2C on a series five 91.

 

is there any way to replace the shielded wire going to the o2 sensor cause mine broke long ago so i spliced it back together and i know this isn't a good fix but i figured it was better than nothing

 

You should connect at the ECU instead of the sensor.

 

Yea, you don't want to disrupt the shielded wire. Theres a reason why It's shielded, tap from the ECU.

 

This comes to my recollection... https://www.rx7club.com/forum/showth...ht=a%2Ff+ratio

 

Did any of you all notice that this is a year old post?