P0156 & P0420

So, having some 02 sensor issues. Had a little rain a few days ago, and two different codes (P0607-control mod performance & P0138- 02 CKT high volts cat 1 sensor 2) and figured something got wet. Went under the truck, found the 02 harnesses wet. Pulled them apart, dried them out, sprayed some electric contact cleaner, then put a little dielectric grease in them. Reset codes, and they went away.

The next day, P0138 popped back up, which is odd, as I run 02 sensor simulators. Checked the log, and the voltage was stuck at 1.2. Only after driving for about 15 minutes would the voltage start to fluctuate normally, then I would reset the code. I could turn the truck off while it’s warm, and 02 working fine, then turn it back on, and I would have to drive 15 minutes for it to start working normally again.

Bought two new 02 sensors (

$49 denso 234-4260 oxygen sensor

denso 234-4260), and started having other codes. So I disconnected the 02 simulator to count that out.
The codes I’m having now:
P0156- 02 sensor circuit malfunction bank 2 sensor 2
P0420- catalyst system efficiency below threshold bank 1.

Not too concerned for P0420, as I’m only running one set of aftermarket cats, so I expected that one, it’s P0156 that is worrying me.

Now, the voltage for circuit 2 will be stuck down at almost 0 volts, then randomly start fluctuating as normal.

Unless I ordered the wrong 02 sensors, but I cross reference the part numbers, I’m not really sure where to go to next.

 

I guess I can check for some exhaust leaks. I know the sensors are in tight, and not leaking there.
I’ll check for signal voltage, too.

Really just seeing if anyone else has had this issue, since it all came up so suddenly with the rain.

 

Update-
I’m curious if the dielectric grease may be causing this issue. I’ve had some issues with control wiring in my field (HVAC) running very low voltage (under 4 volts) having issues with dielectric.

Maybe it’s conducting across terminals, and giving me this issue.

Gonna clean the connectors out, and see how it does.

 

Well, forgot that I’ve already cleaned out the dielectric grease last night LOL

I’m thinking.. I’ve got voltage there at the 02, because you can watch the voltage fluctuate, but only periodically does it drop down to below .01 volts and hangs out there, while the other sensor is fin, which triggers the CIL.

 

Gonna just keep posting here, even though nobody else has responded.
Hopefully this thread will help someone in the future.
——

Once I get off work today, I’ll be installing my old 02 sensor on this bank, since I know that it was working fine before. I replaced both due to the other side sensor acting up.

Hopefully I’ve just got a faulty from the box 02z

 

RESOLVED-

Turns out it was just a crap out of the box 02 that I bought.

Hopefully this thread provides some help for someone in the future.