i just replaced the front 02 sensors last week.
i had all monitors "ready" and no codes after 100 or so miles
then it popped an 1172 code...i knew the spark plugs needed to be replaced so i thought this was probably the cause.
Next it threw a PO150 code bank 2 front sensor...this was the same code that made me replace the sensors last week.
Today i put in new bosch 4's plugs
I cleaned the oil which was on the connector and put on dielectric gease and ran the car again....PO150 came up again.

So next i tried the old sensor from bank 1 which was working when i replaced it.
now it threw a P0155 and an 1172

The original bank 2 sensor which i replaced was covered in carbon whereas bank 1 was clean
when i just took out the new bank 2 sensor to try the old bank 1, i noticed the new bank 2 sensor already has carbon on it after only 450 or so miles.

it throws the PO150 code (pending) after a short amount of driving (10 mins or so)

hope i have not confused you all too much. i'm not the greatest writer :+)

so my main question is...what would cause only bank 2 to soot up?
i'm overdue on my inspection and this is my only car. i have a new sensor coming in the mail. if i put this in am i likely to get the same result as when i replaced both sensors...i.e all monitors ready and no codes for enough time to get inspected.

The inspection is more pressing right now than fixing what is causing soot on bank 2...(i think faulty sensor making a rich mixture)

i read a post here..same symptoms and was fixed with an induction cleaning...i have a can of seafoam...should i go ahead an do the induction clean?

 

I had the same kind of issues after replacing my sensors. One cause was my leaking valley pan gasket that was leaking oil on the O2 sensor connector. I cleaned it, removed it from the engine mount and now have both of them clipped away from the leaking area. This still did not clear up the codes. The solve for me was a full injection cleaning by a garage with BG 4400. They disconnected the fuel line and ran three cans through the injectors. This cleared the codes, ended the carbon build up and the car runs like a rocket. Don't know if this will help you but it worked for me. Simply putting cans of Bg 4400 or techron in the gas did not clear it up. I needed the full treatment which was only $150. I would definitely advise taking it to a mechanic who can read how your mixture is running and how your injectors are performing. If your injectors are clogged your O2 sensors won't function properly, will build up carbon and give you those kinds of codes as your mixture will start running very rich.

 

I think it was a post from you that i was referring to.
I used to have the dealership induction cleaning on my old truck so i know of its effects. I also read a post here a while ago that someone had the same problems as us and fixed it with an induction clean with a can of seafoam.
I'll try the seafoam first, then if it persists i'll go the pro route.
thanks for the reply. much appreciated.

The fact that i had all monitors ready and no codes earlier this week after replacing both front 02 sensors is a little confusing to me. If only i had gone to the inspectors on monday instead of waiting till tuesday..lol, what a difference a day can make!

 

The BG treatment works by injecting it in the fuel lines directly, not sucking it into the manifold the way the sea foam treatment does. By all means, try the seafoam. It didn't work for me but might for you. FWIW, I had absolutely no codes before I changed the sensors. Bang, then the codes. The BG pro treatment cleared up the codes, hesitation at 4000rpm and rough idle problems I've had for two years. Wish I had done it sooner. Best $150 on this truck I ever spent. If you do it, make sure you go to shop that has done it on a Disco. They had to disconnect the fuel line at the pump in the back.