I just got done putting my truck back to 100% stock. I replaced both rear (post-cat) O2 sensors with brand new ones and am getting the following codes:

P0140 02 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)
P0160 02 Sensor Circuit No Activity Detected (Bank 2 Sensor 2)

They come up fairly quickly, usually in just a couple miles of driving. I've cleared them a couple times and they come back quickly.

I have a hard time believing the cats are bad. The y-pipe has been sitting the garage for the last 2 years and right before I removed it the truck passed smog with flying colors. It also smells just fine.

I'm thinking the O2 sensors are either bad or the wrong ones. They came from eBay in a bubble envelope, not even in their boxes.

Anyone have thoughts?

 

maybe the wire connectors are dirty or damaged

 

The connections look good and clean.

 

We're the other senoses turned off? Did you make sure to turn everything back on?

 

What do you mean turned off? Is that even possible? I flashed in a stock tune but I changed the trans segment to 4L80E and a handful of trans-related DTC enablers. But I didn't mess with the engine DTC enablers, those are all stock including those for the rear O2's.

I plugged in EFILive and saw that the two rear sensors are both showing ~450mv ALL the time. This tells me the signal isn't getting to the PCM (if I unplug one of the front sensors it too shows 450 mV).

The heaters in the rear O2 sensors are working just fine though. I bought another sensor from Autozone and am getting the same issue. I swapped the signal wires in the sensor, same issue.

I'm at a loss... I am thinking physical damage to the wires but that is just too much coincidence for it to happen to both rear O2 sensors.

 

I've confirmed that there is continuity in the tan signal wires between the rear O2 ensor and the PCM, and that they are not grounded.

Anyone know where the purple wire goes? My chiltons says it goes to the PCM, but in the PCM pinouts I'm seeing there are no purple wires for the O2 sensor. There is a purple wire for "Low Reference" though.

 

It sounds like they were disabled... Mine are disabled and they show a steady voltage like what you discribed.

 

What do you mean disabled? As far as I know, you cannot "disable" the O2 sensors. You can shut off their DTC and MIL yes, but as far as I know they should still send a reading to the PCM.

Please let me know how you have disabled them. I'm poking around my truck with a multimeter trying to figure this crap out. You might be able to save me a lot of time

I found where the purple wires go into the PCM, they enter via the Blue connector. None of the PCM pinouts show these wires... bizzare.

 

Can you post up your tune? I can look at it later tonight.

 

Attached, thanks!