BMW X5: Limp-Home Mode

If a fault is diagnosed in the system, such as e.g. failure of the high-pressure sensor, the fuel-supply control valve is de-energized; the fuel then flows via a so-called bypass into the rail.

In the event of HPI limp-home mode, turbocharging is deactivated by an opening of the wastegate valves.

Causes of HPI limp-home mode can be:

• Implausible high-pressure sensor values
• Failure of the fuel-supply control valve
• Leakage in the high-pressure system
• Failure of the high-pressure pump
• Failure of the high-pressure sensor

Fig. 56: Identifying Limp-Home Mode Diagram

Fuel System Safety

Working on this fuel system is only permitted after the engine has cooled down. The coolant temperature must not exceed 40ºC. This must be observed without fail because otherwise there is a danger of fuel sprayback on account of the residual pressure in the high-pressure system.

When working on the high-pressure fuel system, take particular care to ensure conditions of absolute cleanliness and follow the work sequences described in the repair instructions. Even the tiniest contaminant's and damage to the screw connections on the high-pressure lines can cause leaks.

Fig. 57: Identifying Fuel System Safety Label

Fig. 58: Identifying High-Pressure Fuel Lines

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