Which O2 Sensor is which?

[Kryptek49]

I've had a couple codes pop up recently - P0133 & P0131 which both relate to an O2 Sensor - Bank 1 Sensor 1. 

 

I've already got a replacement sensor from Zmanalex, however I don't know which one I'm meant to replace.

 

Is it nearside or offside, and before or after the cat?  I think it's Offside Upstream but wanted to confirm before I have to go through the massive PITA to swap it.

 

On a side note - I've only had the car about 6 months, and the previous owner had it UpRev remapped when he had decats fitted.  I'm now back on stock cats, so would Abbey Motorsports not have disabled the pre-cat O2 sensors so that there was no warning light while running on decats?

Thanks in advance

Edited February 5, 2019 by Kryptek49

[ZMANALEX]

Bank 1 is the driver's side on a RHD vehicle.

Sensor 1 is the front sensor in the exhaust manifold.

You will have to talk to Abbey about the rear sensor switch off.