265Service, maintenanceProtecting electronic componentsIn order to prevent faults in electroniccomponents in the electrical system, neverconnect or disconnect battery with theengine running or ignition switched on.Never start engine with batterydisconnected, e.g. when starting usingjump leads.To avoid damaging the vehicle, do notmake any modifications to the electricalsystem, e.g. connecting additionalconsumers or tampering with electroniccontrol units (chip tuning).Vehicle decommissioningObserve national regulations.If the vehicle is going to be parked up forseveral months, the following work shouldbe carried out by a workshop to preventdamage:z Wash and preserve the vehicle –see page 247.z Check preservation in enginecompartment and on underbody andrectify where necessary.z Clean and wax sealing rubber on thebonnet, doors and roof.z Change engine oil – see page 258.z Check anti-freeze and corrosionprotection – see page 259.z Check the coolant level, top up withanti-freeze if necessary – see page 259.z Drain the windscreen wash system.z Increase tyre pressure to value specifiedfor full load – see page 280.Vehicle storagez Park vehicle in a dry and well ventilatedplace. With manual transmission orEasytronic 3, select first gear or reversegear, and with automatic transmission 3move selector lever to P. Use chocks orthe like to prevent vehicle from rolling.z Do not apply handbrake.z Disconnect battery by disengagingnegative terminal from vehicle electricalsystem – see page 264.Vehicle recommissioningObserve national regulations.Perform the following work beforerecommissioning the vehicle:z Connect battery – see page 264.z Check tyre pressure and correct ifnecessary – see page 280.z Fill up windscreen wash system –see page 263.z Check engine oil level – see page 256.z Check the coolant level; top up withanti-freeze if necessary – see page 259.z Fit the number plate if necessary.9 WarningElectronic ignition systems generate veryhigh voltages. Do not touch the ignitionsystem; high voltage can be fatal.