Safety Precautions

Safety Precautions

Note the following when working on the fuel system:


There is a risk of injury because the fuel is under very high pressure.

• Before opening high pressure area of the fuel injection system, fuel pressure must be relieved to residual pressure.

• To reduce remaining residual pressure, lay a clean cloth around the connector and carefully loosen connector.

- Procedures before opening high pressure fuel injection system.

To prevent personal injury and damage to the injection and ignition system, observe the following:

• The ignition must be switched off before connecting or disconnecting injection and ignition system wiring or tester cables.

• Only clean engine with ignition switched off.

• If the connectors were disconnected and the engine was started, then the following faults were stored in the engine control modules: "generate readiness code" in "Guided Functions" refer to Vehicle Diagnosis Tester.


Risk of destroying electrical components when battery is disconnected.

• Observe measures when disconnecting battery.

• Only disconnect battery with ignition switched off.

- Disconnect battery.

Before Opening High Pressure Fuel Injection System


• The injection system is separated into a high-pressure section (maximum approximately 120 bar) and a low-pressure section (approximately 6 bar).

• Before opening high pressure area, fuel pressure must be reduced to a residual pressure of approximately 6 bar.

Note the following when working on the cooling system:


Risk of scalding due to hot steam and hot coolant.

• When the engine is warm the cooling system is under pressure.

• To reduce pressure, cover coolant reservoir cap with cloth and carefully open.


The vehicle could overheat if the cap is installed incorrectly.

• The cap must engage noticeably when sealing.

When working on a vehicle with the Start/Stop System, note the following:


Danger of serious personal injury if the engine starts automatically on vehicles with the Start/Stop System.

• If the Start/Stop System is activated (message in the instrument cluster), the engine can start automatically.

• Make sure the Start/Stop System is deactivated whenever working on the vehicle. Switch off the ignition and switch it on only when necessary.

If it is necessary to use testing and measuring devices on road tests, observe the following:


Distraction and improperly secured test equipment can lead to accidents.

There is a risk that the passenger airbag could deploy in a collision.

• Operating testing and measuring equipment while driving creates a distraction.

• There is an increased risk of injury due to unsecured testing and measuring equipment.

• Always secure testers on the rear seat with a strap and have a second person on the rear seat operate them.

Note the following when working on the exhaust system:


Danger of damaging the decoupling element.

• Decoupling element must not be bent more than 10°.

• Do not load decoupling element on cable.

• Do not damage wire mesh at decoupling element.

Note the following whenever working on the subframe:


Suspension components could be damaged.

• Do not rest the vehicle on its wheels if the subframe mount, steering gear or subframe crossbrace are not installed correctly.

• Do not support the vehicle on the subframe or the subframe crossbrace, for example, by a floor jack or similar device.