Unfortunately my heated O2 connector on the driver side has touched the headers and melted. I've replaced the connector but now the O2 sensor is throwing the code P0134. No activity. I've checked my wiring and I think it's right.

One thing I noticed though is one of the wires on the ECM side had like metal shield on the insulation.

Anybody know what that's for and where I can connect it to? Earth?

 

normally shields go to earth. You may have fried the sensor, are you using the same sensor or did you replace it with new. My son installed a new y-pipe and did not tie wrap the wire away from the front driveshaft and ripped the wires, we tried repairing the wires, but it fried the sensor and replacement worked great. Just a thought.

 

Thanks, I've connected the shield wire to earth and replaced the sensor. Still getting the P0134 error. The output is a constant .99 no many what rpm. I can't see any shield wire on the sensor side of the plug. So it must terminate inside the plug. Time to breakout the wiring diagrams!

 

Have you tried unplugging the sensor and then looking at the live data? Keep in mind, some vehicles have a bias voltage on the o2sensor output. So you may still get a voltage, but if that's the case it will be closer to 450 mv. 990 mv seems like possibly a maximum reading. Is there any chance you accidentally connected one of the heater circuit wires to the signal wire?
The two wires on the o2 sensor that are the same color are the heater wires. Then you have a signal and a signal ground.

 

Yeah, it's .45v, the .99 is the output and it stays at .99 when the engine rpms increase. Not sure what that is measuring but on the other bank it fluctuates when the engine increases rpms.

It's on the ECU side I cut the connector out (leaving about 3" of wires hanging out of the connector to reconnect to) and the wires are totally different colours to the sensor side. Once I got the connector off I was able to cut the melted part off and separate the two plugs. Then I reattached the plug to the wires on the ECU side matching the colours up and I replaced the sensor. I've double checked and it's all correct and soldered up nicely.

I think it something to do with that shield on one of the wires; it's like the shield on a coaxial cable. But as far as I can tell there is no wire with a shield on the sensor side of the connector. So I'm not sure what it does.

 

I say swap the 02 from the other bank and see if the fault follows the 02 or stays at the same side. That will ultimately prove it's a sensor or wiring harness fault pretty quickly.

 

The shielding prevents electronic interference. But I have used generic O2 sensors in the past that didn't have it on the sensor end of the connector and they worked fine. Conversely, when I had to splice my knock sensors they had similar shielding all of the way to the connector (which is all of the way to the sensor) and they just wouldn't work unless the shielding went all of the way to the connector. Several of our wiring setups have that coax looking shielding with the odd looking stranded, bare wire (the other one that comes to mind is the wires to the coils, thought it is spliced and TAPED inside the main harness. There is alot of electrical tape in a stock harness. It is sort of shocking).

 

Thanks Charlie,

I'll expose the shield just before the plug and connect it to where I cut the wire and see if that fixes it.

Best4x4: I've tried two new sensors plus the old one and it's all the same. So I'm fairly sure it's something to do with that shield. I'll try the above first and if that doesn't work I'll swap them over.

 

Ok, that didn't work and I now think that shield does nothing except as Charlie said, prevents electronic interference. It doesn't go all the way to the plug. I checked the other side and it's the same.

When I have more time I'll swap with the sensor from the other side.

 

Did you try disconnecting the sensor, then checking data? If you still get .99v with it unplugged, either the signal wire is shorted to power or the ECU has problems.


One thing you could try is: unplug the connector, put a pin in the connector on one wire at a time and put one finger on the positive battery post. Then touch the pin with a finger on your other hand. Watch your scan data at the same time. When you find the signal wire, you should get a maximum reading on the o2 sensor data pid. Then you can back-probe that wire, plug the sensor in and test the voltage on that wire with the engine running. That way you can see if it really has 12v or .99v or whatever.
I am often suspicious of sensor readings because sometimes the ECU uses substituted values to keep the engine running when it doesn't know what to do with the information it's getting from the sensor. So sometimes the scan data is way wrong.