Oxygen sensor values won't change

[freshlane]

Okay, I have been trying to tune my car and have had no luck due to my 02 sensor running like crap. So... yesterday I decide to take a look at my logger and realized two things. (1) My o2 sensor voltage was stuck at 2.5v, and (2) all of my trims were stuck at 118%. I let the car warm up even more to make sure that it was at operating temp. No change. I figured it was my 02 sensor so decided to go buy another one. I put it in and the same thing. Voltage and trims were still garbage. No change at all. I proceeded to see what would happen if I disconnected the o2 sensor completely & the voltage and trims stayed the same. Below is a list of things I tried

- New o2 sensor
- Checked for continuity between ECU harness o2 signal wire and 02 connecter in engine bay: Test proved good
- Checked o2 sensor connector for power: Test proved good
- Checked 02 sensor grounds: Test proved good
- Removed o2 sensor harness side connector & car harness side connector and directly connected wires (to verify it wasn't the connector)

I do not know what else to do or try. My car is running like crap... and by crap I mean 14.8 - 1/4

 

[steve]

When you are checking the O2 voltage how are you doing it?
Since you reading the trims I assume via a datalogger but which?
Using MMCd you have to look at O2-R for the one and only O2 sensor on a 1G.

Steve

 

[oldman]

Using MMCd you have to look at O2-R for the one and only O2 sensor on a 1G.

Yep, sounds like your 2.5v is read from O2-F.

 

[freshlane]

I'm using a logger with MMCD. I was reading the wrong values. Thank you guys. What about the trim values not changing? About how long does it take for the ECU to calculate those? I waited about 5min.

 

[ekanddsm]

You replaced it and it didn't move,
Check your o2 check connector, single wire on pass side of car under the kick panel.
take off the ecm, key off, and check that wire for contact to any other wire on the o2 at the o2 connector.

then, I would check that same wire(ecm disconnected) turn the key on and see if its getting some mystery voltage.

 

[ekanddsm]

If it start to change values but the trims dont move, reset the ecm then try try again

 

[steve]

The ECU doesn't enter closed loop mode until the engine coolant temp gets over 86F on 91-94 ECUs and something like 106F on 90 ECUs.
At that point the ECU will try to cause the O2 output to switch back and forth but if your tune is too far off the ECU will give up.
If it can cycle then you will see the FTO2 trim start updating based on the O2 Sensor. Once the ECT reaches 186F the ECU will begin to update the long term fuel trims based on the current air flow FTRL, FTRM, FTRH.

Log your ECT, O2-R, FTO2, FTRL from cold startup and lets see what's happening.

Steve