I didn't figure out exactly where the break is. Unraveling the loom was just too time consuming and messy. I know it is between the plug on the valve cover and the ECU, but the harness goes on and around corners so much and splits and joins I gave up trying to find the specific break. I just ran a jumper wire directly.

 

Well I'm glad you posted that factory service manual. I bought an ohmmeter and got the resistant which was OL. I bought a new sensor from autozone from a 1999 dsm which was cheaper 70 bucks compared to 400 for the evo one... I hate SES lights.

 

You can also use a generic 4 wire unit. I used one that cost 40 bucks new. Seems to be fine. One of my other posts about 0031 has the link one of the other gurus gave me. But its a simple ebay purchase. (400 is a retarded price, but it comes with their harness).

 

Yeah I couldn't wait. I like to take care of things ASAP. I should have shopped around more.

 

Resurfacing this thread... I recently installed mods in my sig and got a tune (more than a month now). I've had my check engine light on the whole time. Went to autozone to find out the codes, and have P0031, P0134 and P.... (cant remember). I think my front o2 sensor wires might be broken. The o2 sensor is jammed up against the heatshield, for some reason the Perrin downpipe is located too close to the heatshield. Are there o2 sensors that are not as long ?

Any help would be appreciated

 

The 02 sensors as far as I know are all the same. You should modify the heat shield, that would be more common. Find out from Perrin what should be done if you can.

You also want to make sure the o2 wire is not resting on the rear of the radiator, which I have seen in some modded setups.

With having a number of codes you need to suspect something else however. With one code you can usually pin down the root cause, but with a number of them you can have a lot of false positives wasting your time. You need to get all the codes, and look them up, and be able to reset them. Then see which one fires again first.

Its a pain in the butt, but I am an ecuflash/evoscan guy and that is one of the advantages of that setup. Find a buddy that has a laptop with those tools, and buy him lunch. log, write em down, clear, then let them pop back up, and write them down again. This eliminates old ones you had that are obscuring your current issue.

 

thanks for the advice! I'm going to clear all the codes with my buddy's OBD scanner, and then see what happens. I think I need to modify the heatshield quite a bit to make sure the wires are not bent. Will update after this weekend when I work on my car

thanks again

 

Im going to be chasing the same issue myself, I have been researching where common problems are with the harness. There isnt much information but this thread has helped me out enough to get motivated to test things out. For now I disabled the code in the periphery bits. However I would like to get back on CL before I make some major tuning changes.

 

Even though I get the p0031 code, does that mean its really the heater circuit? I am really trying to get closed loop to function and after replacing the sensor with oe i get the same code. I multimetered the circuit and Im getting 12.2v in the heater circuit. What next? Doesnt appear any thing is wrong to me!

 

Not sure if I was clear in the posts of this thread, because during this troubleshooting I hopped around in a bunch of threads. So just in case it gives you and idea, my actual problem was that the larger thick wire that goes from the ECU to the front 02 that is green is shielded. So wrapped in another grounded wire to protect it from interference in the readings. The EE guys could explain it better. The The other positive wire of the 02 somewhere in the harness between the ECU and the valve cover plug is (was) grounding out on that shielding wire. A bit of testing with a voltage meter eventually demonstrated the grounding on what should be a positive.

Once I was relatively certain I cut the wire that was being grounded that shouldn't be and ran it directly to the ECU. No CEL again after that. Then I tried to chase down where the break was allowing the grounding but the loom has too much tape and bends and wraps that it wasn't worth it. I just ran a permanent jumper wire to resolve.

So, check that the four wires on the plug at the valve cover are reading as they should be expected to. If you need help figuring out what that is let me know. I have it on one of my posts about this problem with screen shots of the wiring diagram that someone got for me. I used that info to confirm the grounding of an inappropriate wire.

 

That's my issue. I got to look for the diagrams yet. I'm picking voltage on a ground. I will have to look for the pin orientation on the valve cover connector

Continuity test shows ground when power off but 12 v when power on

 

In post #3 I have a pic from the manual I used to test. However I got details on the ecu side from someone to test and that is how I also found voltage on a ground. It sounds like the same issue or similar.

I looked through my old posts, which you can check by going to my statistics in my profile easily. I didn't find what I was expecting though. I will have to check my work bench tomorrow, as I might hav printouts I created while solving this years ago. I also need to find the pics for my broken links in that other thread which will help me remember what wire should be sound what.

Worst case I can unplug my o2 connector and test with the meter and tell you what is what. I know it's working well now.

 

A definite answer on the pinout that is confirmed would be nice, if you could provide!

 

really just need help identifying pins, I have the FSM and Ive been viewing it.

I need to know how the pins are laid out 1,2 3,4 clock wise or counter clock wise left to right etc..

does this diagram look right?

 

211ratsbud. Sorry for the late response. I did find what I have left as a note on this troubleshooting I did many years ago. Its kind of craptacular, but it will give us some direction. I went down to my car and took the connector out and retested according to my own notes.

With the connector on the valve cover disconnected I was told to do the following tests.
(in my scribbles image below)

Disconnect O2 sensor
1 - Test across 1 and 3 pin. It should read between 6-20 Ohms. Mine read 9
2 - Turn on Key (don't start engine) and test for 12V at #3pin. Ground on any nearby chassis bolt. Turn off key
3 - Measure resistance from #3pin back to the ECU pin. (71 from the FSM). It should read 0 Ohm.

I did these just now, and confirmed my working setup did this as noted. I will try and find the email or PM that some guru sent me that had these notes in case there is more detail. However that is what I kept, so from that I figured out that my pin.

How those tests told me that pin4 was grounding, I don't remember.

Now if you look at the plug that comes from the harness, this is how I numbered them.


When you look at the rear of the plug, you will see a covered up solder job with a couple of zip ties. I don't recall if 3 or 4 goes back to the ECU, but you should be able to tell via the color of the wire.

So you notice that the plug is turned down, but you can see that the Purple wire has zipties on it, because underneath I soldered that Blue wire that goes directly back to the ECU. Somewhere between that connector and the ECU that wire grounds out

1 = Black
2 = Red
3 = White (#71 on ECU)
4 = Purple with a red stripe ( I think ) Its all covered up.

Another image of the rear of the plug.


See if any of this helps you, and tomorrow I will try and get some time to confirm where in the ECU I jumpered that #4 to. What pin, because ultimately I think that is what you are asking me. its taken me a while to ramp back up on what the h@ll went on when I was working on this. I will take my ECU out and take a photo of the rear so we can confirm which pin my jumper blue wire goes into.

Hard to read notes image