ok i think this should be a nice easy one for you all.

[Big_A_Cupra20vt]

i have a vag com error code 17511 o2 heater circ, bank1 sensor 1 performance to low (sporadic). and 16795 secondary air system incorrect flow detected.
i know the second one was a split hose and that is now sorted, and the first one is something to do with lamda but not sure what the lamda sens actually does and what problems this can cause if not sorted out. can someone clear that up for me please.

 

[Beaker™]

I'm sure sensor 1 is the pre CAT sensor. If so, its function is to asess the state of your exhaust gasses before they pass through the CAT (ie a true reading). The ECU uses this info to adjust fueling.

Probably best to get it replaced sooner rather than later as if it gets any worse you'll go into permanent limp mode. IIRC pattern parts are iffy so probably best to get a ganuine part. Circa £100 i think.

 

[big eck]

I had the exact faults on mine mate, fixed the air system no bother it was just a loose hose, the lamda your lookin for is the one BEFORE the CAT.

They cost £100+VAT from the dealers

I managed to haggle mine down to £100 all in

 

[Big_A_Cupra20vt]

ok cheers guys ill ill get this sorted out in a couple of weeks then. think im gonna get all hoses changed as they all look a bit dodgy and brittle.