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 bonnetIntroduction
This chapter contains information on the following subjects:
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→ Applications (apps)
Information on the mobile online services Car-Net and applications (apps) can
be transmitted directly to your vehicle and integrated.
Information on Car-Net services and application ...
Refrigerant Circuit Connections with Valve for Switches
Note
For switching pressures, removing and installing switches
and switch arrangement and version, see vehicle-specific
refrigerant circuit.
Refer to
→ Rep. Gr.87.
...
4-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.
...