I'd say it got two front sensors yes...

I'm afraid I can't find the gearbox/engine-codes, it's absolutely impossible to access them from above, the manual shows where they should be but I can't see any of them, maybe if I hoist the entire car up I could access them from below...
So I can't say if ...

Well, cost is a factor and I guess Bosch's are a bit cheaper than originals,
I have this LS07 0258986507-36Y replacement that should be the correct one, however the connector isn't the same.
First of all I needed to know which one the P0135 Bank1 Sensor1 is supposed to be, then I can try to find a ...

I'm having this problem with my 99 S80, display is showing emission problems, the lambda light is on.
OBD test shows code P0135 "O2 Sensor Heater Circuit Malfunction Bank 1 Sensor 1".

Which sensor is this, the one towards the front of the catalyser?
What's the pinout of the connector? I got two ...