Supply Pressure – Fuel system
Make sure there is fuel and bleed the fuel system. Check whether any of the overflow valves is opening too early. Check whether the fuel shut-off valve is closed. Check whether the fuel filter is clogged. Check the feed pump. Make sure the fuel system is not leaking. If the fault code is generated while the engine is coasting, i.e. when driving downhill with the accelerator pedal released, you can look at "Stored operational data" under the Supply Pressure tab for help with troubleshooting.If the feed pressure deviation has been -1.0 bar or more during a certain time period, it is a sign that the fuel filter is starting to get clogged. If there is only a slight deviation in supply pressure, this may mean that the overflow valve is seizing. To check that the fault has been rectified: Switch on the ignition power and wait for at least 15 seconds. If the fault has been rectified, the fault code becomes inactive. Clear the fault code. Switch the power off and on with the starter key three times in succession at 10 second intervals to extinguish the warning lamp.
What you'll see
No driver-visible symptom recorded.
System reaction
For the fault code to be generated, the supply pressure must have been lower than permitted for at least 7 seconds. The time limit has been set so that the fault code will not be generated in the event of a brief pressure deviation which is not caused by a fault. If the voltage is outside the permitted range, the control unit uses a preprogrammed value. The maximum engine torque is limited by approximately 40 % as long as the fault is active. The fault code may "cure itself" if the fault is only temporary. The fault code will then be erased from the fault code memory after a period of time with no problems. The fault code affects the vehicle's emissions of nitrogen oxides (NOx) and the lamp which warns about a high level of contaminants comes on in the instrument cluster. A text message is also displayed on vehicles with NOx control. Vehicles with NOx control An active fault code cannot be deleted from the control unit. When the fault has been rectified, the control unit must verify that the fault has been rectified in order for the fault code to become inactive.
Diagnostic depth
The feed pressure has been implausibly low in comparison with the nominal pressure for various operating conditions.
The fault can be due to any of the following causes: - One of the overflow valves open too early. - The fuel shut-off valve is closed. - The fuel filter is blocked. - Air in the fuel or out of fuel.- Defective supply pump. - Serious leakage in the fuel system.