Bad Sensor Wiring? P0136.

[Artago]

Hi all I'm having a bit of a problem here and I need your help. My car is throwing a P0136 (has been since I bought it) error code. Correct me if I'm wrong but this is the rear O2. So I replaced the sensor with one I got from Spark plug, Spark plug wire, spark plug gap, spark plug cross reference and ignition wires at Sparkplugs.com and car is still throwing this code.

Now, a little background. While tapping the front O2 sensor signal for a A/F gauge I noticed that the wiring harness looks like it has been tampered with (most likely by the previous owner of the car). But I don't know for sure. Can you all look at this pics and tell me if this is how it's supposed to look like? And if everything looks like it is connected correctly.

If not, how do I go about connecting the wires properly. Or better yet, how do I go about testing the circuits?

NOTE: The Brown wire with the Blue wire tap is how I tapped my front O2. It's all good.

Click on the pics for larger version.

[Artago]

More pics.

[turboglenn]

Reconnect the cut black wire. It may be the ground for teh rear sensor. You can get teh ECU pin out on vfaq.com ( but it doens't show teh sensor grounds )I just chekced. I would say resolder any cut wires and remove any "extra" wires you didn't do yourself. Also, i'm not sure what eh # for teh code is, but a gutted cat will throw a rear O2 sensor code as well.

[Artago]

Originally Posted by turboglenn

Reconnect the cut black wire. It may be the ground for teh rear sensor. You can get teh ECU pin out on vfaq.com ( but it doens't show teh sensor grounds )I just chekced. I would say resolder any cut wires and remove any "extra" wires you didn't do yourself. Also, i'm not sure what eh # for teh code is, but a gutted cat will throw a rear O2 sensor code as well.

Hey, Thanks for the quick reply.

I'm not sure which black wire you are referring to. Infact all the wires are connected to something it's just a jumble.

I don't have a gutted cat but I do have a OBX high flow cat. Could that be throwing the CEL on a brand new sensor? BTW P0136: O2 Sensor circuit malfunction (Bank 1 Sensor 2).

Few more questions. Could this bad sensor signal from the rear be causing me to fail emissions control? I just went for emissions control and failed (with a new motor with 272 cams). Or could it be the faulty ISC that I have (I ordered a replacement, which is coming in the mail).

I just need to pass emissions control and I was wondering if this faulty rear O2 signal could be the culprit. I heard that the rear O2 has no bearing on fuel injection maps or emissions. Could the faulty ISC be the reason I failed or is it something else?

PS: Sorry about this thread being all over the place, I'm trying to trouble shoot several problems and I don't know if they are connected in some way.