The fuel pressure sensor measures the current fuel pressure in the fuel rail very accurately and quickly and delivers a voltage signal to the IDM in accordance with the current pressure level.
The fuel pressure sensor signal is used to:
โข determine the injected fuel quantity,
โข determine the start of injection,
โข drive the fuel metering valve on the high-pressure pump.
Effects of faults
The fuel pressure is a critical value. If the signal should fail, it is no longer possible to carry out a controlled injection process.
Short circuit/open control loop:
โข In this case the IDM assumes a pressure of more than 2000 bar. In response, the injected fuel quantity is set to 0 and the engine cuts out or cannot be started.
The injected fuel quantity is also set to 0 if values are implausible.
Diagnosis
The monitoring system checks:
โข for short circuit to ground/battery and open control loop,
โข for plausibility (required pressure from the timing map to the pressure actually set).