Just purchased a 2007 F150 crew cab 5.5 bed 4x4 with a 4.6 triton 210k miles that’s been well maintained. Recently had intake replaced, induction module replaced, 2 COP replaced in last 6 months, evap module replaced, and tank pressure sensor replaced. All the codes were gone after those repairs I’ve been told. Before purchasing the vehicle I scanned it and it showed 3 codes, P0308 misfire on cylinder 8 and P0135, P0155. I replaced the COP #8 and that code cleared out leaving the 2 other codes. I replaced all 4 02 sensors with Bosch direct replacement. Cleared the codes and they came back. I’ve checked all the wiring and can find no problems. There is 12 volts present at both upstream heaters. Both heaters are heating up. You can feel them heating with your hand and see them with a flir thermal scope. I’m getting varying voltage feedback from all 4 sensors between .1 and .9 volts. I’ve reset the KAM. I’ve unplugged every sensor on the same circuit with the 02 sensors and tried to clear the codes. I get the P0135,P0155 codes along with whatever other sensor I have unplugged. The only thing I can see missing is there is no amperage draw showing on my snap on edge scanner for the 4 heaters but I’ve been told the pcm probably doesn’t support that.
I’m stumped and everybody I know is somewhat stumped on this one.
Anyone run into something like this before ?
The truck runs fine besides a slightly rough idle and seems to get less than expected gas mileage on the first 1/3 tank.
Its not going into closed loop and I’m concerned about damaging the cats if this is left unsolved.
Any help would be greatly appreciated
Many Thanks

There is a head temp sensor that is on a common feedback splice return wire to the pcm along with several other sensors, which are all of the sensors I unplugged to see if one of them could be the problem. The heaters are all turning on as soon as the ignition is turned on, you can feel them physically heating up as soon as the key is turned on and they are all showing on via my snap on solus edge scanner watching the pcm. If the codes are cleared they will return approx 5 seconds after the truck is started or if they are cleared while it is running they will return approx 5 seconds later.

I went and purchased a new OEM ford O2 sensor and put it on the drivers side. Cleared the codes and started the truck. Approximately 5 seconds later I had both P0135 & P0155. I cleared the codes with the truck running and approximately 5 seconds later both codes were back. Exactly the same results as I had with both sides having the Bosch sensors. I could feel the ford OEM heating up hot, and it showed white hot on a flir thermal scope up in the O2 sensor. The sensors are heating up.