You should have Bank 1 sensor 1 - A/F sensor ( upstream / before cat ) & Bank 1 sensor 2 which is the actual O2 sensor, downstream/ post cat.

 

Thanks guys. I didn't have upstream/downstream on the menu but did have the aforementioned sensor 1-4. Assuming sensor 2 is the one we're talking about - that one did change to a reading when car started unlike others that stayed on blank (-) but it stayed at 0.00. Dead sensor or bad reader?

 

Scrap that. Tried again today after a drive. Results uploaded here:
http://postimg.org/gallery/d3t7znk2/9792e8fc/

 

So further testing... When driving along the graph is fairly similar between the two sensors. When still the second stays fairly steady and the other still goes up and down. Assume thats the correct way to text and it's not the ***** lives on?

 

Set up so your looking at bank 1 sensor 1, that's is what is going into the cat, and bank one sensor 2, that's what is coming out. Properly processed exhaust by the cat should read steady at 0.8v ish. Also, hold your RPM around 1200 to 1500. Takes a few minutes for the cat to fire off and everything to wake up.

 

Thanks sparky. Ok so took it for a ten min drive then tried it holding the revs between 1 and 1.3. Sensor two went between 0.5 and 0.7 and sensor one went up and down consistently. When not reving the engine sensor two stayed at a flat rate and sensor 1 continued to go up and down. What do you think?

 

If 2 didn't follow 1 like a mirror image, you may be looking at a lazy O2 causing the code after all. Long live the puss.

 

That's great news! Any guesses which sensor could be bad? If I just keep clearing fault code will I be doing any harm to car by continuing driving or is important to get sorted soon?

Found sensors on eBay quite cheaply so might look to get one there. Is it quite a hard job? I don't think I have the tools or know how to do myself but always good to know before I ring the garage how long they should be charging for, been fobbed off far too many times before!

 

The post, down stream, bank1 sensor 2, whatever you want to call it, appears to be the lazy one. O2 socket can be purchased without dipping into your Christmas account and changing it out is fairly simple.

Side note. Have had some bad times with "cheap" sensors.

 

Thanks so much for everyone's help. I'll get the o2 changed and hopefully that'll be the end of it.

Cheers all