Although unusual, it is not uncommon for the crank position sensor to fail.

Symptoms include:

• Uneven idling
• Idle dipping to below 500rpm then recovering
• Uneven acceleration
• Low engine running time
• Engine stalling
• Fault codes reading from P0335 to P0339

The part number(s) for a replacement part (same for both 600 & 700cc cars):

• Bosch: 0261 210 142
• Merc: A 003 153 95 28

The tools required to replace the sensor are:

• 7mm socket (for hose clips) (or philips screwdriver)
• 2x flat blade screwdrivers
• T30 torx bit
• E10 socket

 The sensor is located on top of the block pointing down into the bell-housing.
First unplug the intercooler fan.

Use the 2 flat blade screwdrivers, to first lift the vertical clip on the top of the intercooler fan housing, then push in the 2 side clips, and pull the housing forward, it will appear to pivot on the bottom of the fan housing.

Pull the housing up and out, the bottom of the housing is not fixed, but it has 2 tabs which locate onto the intercooler itself.

Remove the top intercooler pipe hose clip.

Remove the bottom hose clip and pull the pipe away.

We're leaving the bottom hose in place for now, only because we can create more room by removing the throttle-body.
Use an E10 socket to remove the 4 securing bolts shown.

Unplug the throttle-body connection.

Remove the hose clip from the bottom intercooler pipe.
You do not need to remove this pipe completely as there is enough flex in the pipe to pull it clear.
This has the added advantage of not having to remove the rear panels to gain access to the turbo connection.

Now remove the intercooler, it's held in place by 4 tabs as shown, these can just be pressed in with your fingers as you pull gently on the intercooler to lift it from the mount.

If you want to give a little bit more room to pull the intercooler out of the way, you can unplug and unclip the vacuum pipe from the top of the inlet manifold, this will give you about another 10mm clearance.

We found the easiest technique in removing the intercooler is to pivot it up from the top, so pull the bottom of the intercooler out first as shown below.

You can now see the sensor, remove the connection circled here.

You can 'just' fit a T30 socket into the retaining bolt at the back of the sensor.

The sensor will just pull out.
We have heard of these sensors getting stuck in position, this may be down to trying to remove them at the wrong angle, but gently twist the sensor to break any seal which may have formed.

Replace, and refit in reverse!