First of all thanks Hans, Steve, Marty & others for chiming in on all of my threads. You guys have been super helpful. Thank you.

Last week I posted about my rear 02 sensor throwing codes @ me as soon as the car turns on.

The code is...
17526 - Oxygen (Lambda) Sensor Heating: B1 S2: Open Circuit
P1118 - 35-00 - -

Well the car is currently up on jackstands getting a suspension refresh (waiting for parts) so I really had an opertuninty to try and figure out whats going on.

I pulled my rear o2, looks BRAND NEW. Checked the wires, there are two whites, a grey & a black. So four total. These colors all match up to the existing harness I have them soldered onto.

I pulled the front o2 sensor and it LOOKS BRAND NEW AS WELL! My god, they have 20k on them I figured they would be black. These sensors look just as good as when I put them in almost. Just a little cleaning made them that bronze color again.

Well the test I did was I swapped the two sensors to see if the code travels with the sensor or not. It doesn't. With the front sensor in the rear location I had the same code that appears above. So I'm going to predict that my 02's are in great condition, my wiring harness or ECU must have a fried connection???

I am not running any spacer setup currently and will be experimenting with that tonight. I have waynes o2 block and a few spark plug gappers.

Any sugestions on where I can go from here?

Should I do a line test to see if the wires reach the ECU? Does anyone know what pins they hook up to? They are numbered on the rear 02 harness 1-4. I doubt they are 1-4 on the ECU as well, haha<ul><li><a href="https://forums.audiworld.com/tt/msgs/1794536.phtml">Previous Post</a></li></ul>

 

I would check the wiring harness going to the ECU for the rear o2 sensor . IF the connections are good there then open up the ECU and start checking there. I know it sounds ridiculous like what could you see in the ECU, but I found a broken contact on one of the etched wires in my ecu, I got some 30 gauge wire and fixed it and now it works like a charm!

I would start with the wiring and then go from there. I became fairly intimate with the diagnosing process of an O2 circuit so I might be able to lend more specific advice if you need it!

Carl

 

reaching temp, which is most likely due to a wiring issue. Either you have a broken wire, or the connector is bad, or something like that. Since the sensor swap didn't find an issue, it is not in the sensor or the pigtail on the sensor. Check continuity of each of the four wires upstream as far as you can trace them. Also, both white wires are ground. If you can, swap them on the sensor pigtail to see if the fault moves from a heater fault to a reading fault. If it does, then one of the white wires is broken, if not, then it isn't a ground line issue, but the black or grey line (I don't know which is the heater).

 

set to the ohm setting to check the continuity in wires...

Two of the terminals from the rear o2 harness (car side) were in contact with each other it told me. Is this right? I Guess I will have to tear that wire out tonight, I want to pass inspection before H20!!

 

open circuit, definitely leads me to believe th ECU is not seeing it at all....
So i am clear, which o2 sensors did you go with??? The generic Bosch?!?
Your sure on your wiring, correct?

You can also confirm there is juice coming through the harness to s2 by putting a volt meter on it. You should get random fluctuations to 1 volt (IIRC)...Confirm the heating element as well, with just the ignition on....

It would be unusual to have to rewire something in the ECU, but not out of the realm of possibility....

Use Waynes adaptor, and make sure it is all snugged up so there are no leaks...
Be careful not to bang the tips of the sensors, i ruined 1 or 2 by dropping them...;-(

 

Check contact 3 and 4 (car side) for voltage with the ignition on (car does not need to be running). You should be getting about .45 volts. If the wires are in fact shorted to each other, you can unplug the ECU and check continuity between the wires once more to see if the short is in the wiring or the ECU...... I would be surprised if the short is in the ECU.

I would be happy to talk it through with you if you would like... I know how much a PIA that whole process is as I spent a couple of weeks diagnosing it and was so happy when I solved the prob.

Carl


**Edit, I just realized that your open circuit is with the heater not the signal line... with that in mind, start the car and check the #1 and 2 terminals for voltage, you should have about 12 volts

 

crdouglass3@gmail.com

 

show as shorted (correctly)...

 

vag shows the voltage and all heater element info, I posted it above. I'm going to do more investigating tonight!

Thanks!!

 

YGM!