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The article below describes how I replaced the Lambda Sensor (or Oxygen Sensor) on my own Audi S2.

No responsisbilty is accepted for anyone attempting this procedure by following the steps contained in these pages. This is intended as a guide only and all usual precautions should be heeded when attempting work on a motor vehicle. I cannot be held responsible for any damage sustained as a result of using these pages.

Tools needed are as follows:

1. Lambda sensor removal socket. I used a Draper 55540.
2. Flexible extension bar
2. Replacement Lambda sensor (Audi Part number 034 906 265 C. Bosch Part number 0 258 003 957)

First step is to raise the bonnet of the car. You may want to consider disconnecting the battery. When the bonnet is open, the courtesy light in the boot comes on. Disconnecting the battery will prevent the current drain. An alternative is to pull fuse #4 from the fusebox.

Upon raising the bonnet you will have the view seen here on the left.
The lambda sensor is screwed into a threaded boss on the exhaust downpipe,
just below the airbox.

The lambda probe has wires which are routed
under the airbox, round the suspension turret
and connect to 2 plugs which are located just
behind the strut brace. You can see them here
attached to a bracket. They just pull apart.
The wires are secured by tie wraps which can
be undone to release the loom.

With the wires loose, it is necessary to place
the socket over the old sensor and attach the
breaker bar for removal. There is very little
to work in here which is why a bar with a flexible
head is needed. The socket I used was 3/8 drive
which made it easier to attach the bar. It may
also be easier to lift the airbox heatshield

One turn of the bar released the old probe easily.
It was then possible to remove it by hand and
thread in the new probe. The new probe should
have G5 anti-sieze compound added to the threads,
if not done by the manufacturer. DO NOT allow grease
to enter the slits of the probe. Tightening torque
for the new probe is 50 Nm.

The old probe can be seen here. It is in poor condition
and by the looks of things original as it has an original
Audi part number on it - 077 906 265. Recommended change
interval is every 60k miles regardless of usage.