Daily driver in Ireland


Starting this thread to document and get feedback for the work that needs to be done on my recently purchased A2 that I'm planning to use as a daily driver.

Got the VCDS laptop up and running today and I cleared the codes and pulled the fresh ones. When I got the car it had engine light on and the previous owner said when the light came on he replaced the lambda sensor (for which I got the receipt) but the shop did not clear the code.

Anyway, the car is running decently, but apparently there are things that need to be taken care of. The codes I get are the following:

5 Faults Found:
16555 - Fuel Trim; Bank 1
P0171 - 35-00 - System Too Lean
16786 - EGR System
P0402 - 35-00 - Excessive Flow
17586 - Linear O2 Sensor; Pump Current
P1178 - 35-10 - Open Circuit - Intermittent
17589 - Linear O2 Sensor; Reference Voltage
P1181 - 35-10 - Open Circuit - Intermittent
17604 - Oxygen (Lambda) Sensor Heater Circuit: B1 S1
P1196 - 35-10 - Electrical Malfunction - Intermittent
Readiness: 0010 0101

What would be the proper way to tackle this? I believe a new sensor is imminent, where do you get yours? From what I gather it is very sensitive about the sensor being used. What about EGR? Thanks!

So there are two sensors for the 1.4 petrol for both AUA and BBY. One is just before the exhaust manifold cat and the second one just after the mid exhaust section cat.

You can put the codes into the Ross Tech wiki to get more detail about what they mean but before condemning anything it might be worth trying CataClean or similar product and remaking the connections to the 2 sensors in case they have any oxide built up on the pins.

Should you need to by lambdas, consensus seems to be that NGK are the ones to go for from what I have read on the posts on this forum

Part numbers:

036906265J Pre CAT Lambda
036906265H Post CAT Lambda


Thanks Justin, sounds like a sensible way to move forward before investing in new sensors. I'll dig in to find more details about the codes.
Ok, spent some time researching this, EGR valve cleaning + checking the wiring will be the first step. Found a good guide for BBY engine:

I'll give it a shot with cataclean, in any case none of these issues are critical (?), I just need to sort them out before the next MOT. I'll check the MAF sensor tomorrow and for possible leaks.
Last edited:
The pre cat lambda adjust injection duration, in conjunction with the MAF sensor, to give the right mix for efficient combustion. Post cat checks efficiency of the cat. If tailpipe emissions are OK (from your version of MoT), then look at the pre cat lambda first. You can look at each lambda with vcds. Don't know the group/block numbers, but this will help.
Thanks Mac! The car passed the emissions test two months ago in this condition, so this is a really good tip.