So, what happened? What is the front O2 voltage on your scan tool showing now?


You do have a service manual or wiring diagrams for the car, right? Its not uncommon to have 1 power wire: ignition 12v, sensor ground, heater ground, signal out is one way Ive seen a 4 wire O2 done, but you need to see which pin (or wire color) is which to verify every one.

Once all is verified as good, plug it back in and backprobe while running for the signal output wire (as that line will be dead on the car side until the sensor is plugged in and sending signal through it).

If everything is good there, but you're still not getting proper signal at your scan tool, you can move back to the signal wire coming into the pcm and check that for proper O2 signal (to determine if the fault is inside the pcm or in the wiring between pcm plug and o2 plug).

 

This is what i got just now. Checked everything and sprayed starter fluid and no change in rpm. So what could be wrong here? The O2 sensor readings are acurate so its getting power.

 

Did you go through the o2 plug pinout and confirm all 4 wires are good as I'd noted?

You're saying the O2 sensor value is 0.5, is that with your scan tool at the pcm or measured with a multimeter at the O2? You also say the reading is accurate, but what does that mean - accurate in that the multimeter reading matches the scan tool / pcm? Reason I ask is that's not a correct output for an O2 sensor. Once it gets to closed loop mode (which it should be with 200F ECT), that sensor should be oscillating from about .1 to .9.


One other unrelated question, has the MAF always shown 0hz? If so, that system appears dead too (although it can run on MAP alone as you've found, so its also lower in priority than getting the O2 up and running again).

Edit - One note too - those LTFTs are likely pegged full rich (ie the computer is maxed out full rich within its adjustment window trying to keep the car alive). When you do future readings, its best to include the STFT value as well because that shows the adjustment the computer is trying to make right now and is more indicative of current conditions.

 

The O2 readings i got where the 3 top of page and the fourth is the ground correct? Also guess sometimes i should clarify a little more. But the readings i get match the scan device. Now in just get the (O2 doesnt change code.Found another wire though i included pic. Must have missed it somehow but it was in the big bundle in pic. I could find nothing on that drivers side i would connect to so confused on that one. If you have a bluetooth connector for the car. The app i use is gatage pto. Thats ehere i reset and basically everything and the 0.5 reading was rounded up from 4.97 i think without looking. It was with multimeter and matches scan tool.


Just so you can kinda get what im seeing

 

 

 

Last note...all the sensors in the pic are new including egr valve

 

I wasnt entirely sure what those numbers meant.

WhIch measurement corresponds to which wire function (including units)? I know there are a few configurations of wire setups for 4 wire O2s, and I can't remember what it is for these cars.

IE - ground wire is 0.001 ohms to ground terminal, power wire is 12.2 volts, etc.

I'm not following this either - how does 0.5 round from 4.97?

If the multimeter for the signal wire matches what the pcm is seeing, thats a good sign that you at least have 1 good wire in there. But we need to figure out why its stuck and not oscillating voltage like its supposed to. That's why I'm curious about the readings on the other 3 wires. I'm wondering if the heater side of the circuit isn't completed / the sensor isn't getting hot enough to start working.



On a separate note related to the new 'bonus' wire - are there any engine wiring harnesses available locally via junkyards? You've now got 3 wires not hooked up, plus the cut up EGR, plus whatever other surprises are lurking. Id be very leery that there are more issues with it that you don't know about yet. Just might add some peace of mind and simplify some of the later troubleshooting if theres one close by thats reasonably priced.

 

I have not, but they do sound VERY helpful!

 

I am in the same boat. I believe I found and posted last night the first two mystery wires might be for the evap purge solenoid (which explains one of the engine codes). The new mystery wire.... I am trying to figure if it is yellow/black or tan/black. I think it looks yellow/black in that pic. Looks yellow/black and looks like it comes from the back of the engine. If so, I wonder if it is a wire for one of the ICM connections. I would check any plugs within the reach of that wire if one is missing a connection.