Dodgy O2/Lambda Sensor

[Crasher]

Avoid taking out and re-installing a Lambda sensor especially if you do not have the correct specification grease such as aluminium or Nickel based extreme temperature types, NOT copper grease! This is because the threads are short and not designed for multi use, strip the thread in your DPF and you will regret trying to save £100 on a sensor when paying for the DPF to be removed, repaired and re-fitted. Also a warning about aftermarket lambda sensors. We will only use Bosch (or NTK where appropriate) and there is nothing wrong with them but we are increasingly having to reject sensors delivered by motor factors as when we get them it is obvious they have been used before and in two cases we have found cleaned up old sensors in the box, only accept sensors that come in a correctly sealed Bosch box with the tamper proof seal intact. In fact second hand parts that have been returned for credit being sent out to us is becoming increasingly common, it has even happened twice from TPS! This isn’t the suppliers fault but that of scumbag garages sending parts back and the collecting and return department staff not being vigilant.

[johnro79]

Hi there
Could you tell me the location of it please?
I bought a new one and want to replace it on Tuesday but don't know where to start....
Thanks for your time

[Crasher]

It is in the cat/DPF directly after the manifold flange and before the cat element, this is on the cars right adjacent to the right inner wing, it must be one of the easiest I know to get at.

[lozzyho]

Johnro, really sorry but I COMPLETELY forgot to send the sensor. Totally slipped my mind.

Apologies, mate.

[Renars]

If you lift throttle on modern diesel and coast in gear, there is no fuel injected at all.

[lozzyho]

I suggest to scan it with VCDS as something else or different may also pop up.
If you lift throttle on modern diesel and coast in gear, there is no fuel injected at all.

Yeah that was exactly the symptom with my a6, Renars. Faulty o2 sensor though.

[Renars]

Yeah that was exactly the symptom with my a6, Renars. Faulty o2 sensor though.

Looks like in other driving conditions car would not recognize faulty sensor yet.
Was sensor well accessible ?

[lozzyho]

Yes, absolute doddle to access and replace.

Open the bonnet and look at the engine cover. Directly to the left of that you'll see the DPF (a metal cylinder). The o2 sensor is in front of the DPF, screwed into it at the point just before it gets fat.

Very technical description I know!