The following steps should always be carried out in the specified order before working in the engine compartment :

Park the vehicle on a level and stable surface.

Depress and hold the brake pedal until the engine has stopped.

Apply the handbrake firmly Braking, stopping and parking Brakes Parking .

Select the neutral position or move the selector lever to P Changing gear Changing gear Automatic gearbox see Automatic gearbox_0 Automatic gearbox see Changing gear_0 Automatic gearbox Manual gearbox see Changing gear_0 Manual gearbox .

Stop the engine and remove the key from the ignition Starting and stopping the engine Engine and ignition Ignition see Engine and ignition_6 .

Allow the engine to cool sufficiently.

Children and other people should be kept well away from the engine compartment.

Ensure that the vehicle cannot roll away unexpectedly.

WARNING
Preparing the vehicle for working in the engine compartment
Opening and closing the bonnet4-Pin Heated Oxygen Sensor (HO2S), Removing and Installing
Note
Do not repair the heated oxygen sensor wires. Repairing may
result in malfunctions.
Use the faulty sensor as a guide for installing all of the
accompanying attachments, cable ties or marking bands.
...
7-Pin« Trailer Socket
If more electrical consumers need to be connected than the
»7-pin« socket allows, a second
»7-pin« socket must be installed.
Pin assignment must conform to DIN ISO 1724:
1 - Left turn signal
2 - Tail ...
Electronic immobilizer
First read and observe the introductory information
and safety warnings The immobilizer helps to prevent the engine
from being started and driven with an unauthorised vehicle key.
There is a chip in the key. It automatically deactivates the immobilizer when
the vehicle key is inserted into ...