Fuel Rail Pressure Sensor

Fuel Rail Pressure Sensor

High/Low Input Failure
These are continuous monitors. The voltage from the sensor is compared to a failure threshold defined in the software. If the voltage is below the low threshold, then a timer starts to increment. Once this timer exceeds another threshold, then a failure flag is set and a DTC is stored. If the voltage exceeds the high threshold defined in the software, then a timer starts to increment. Once this timer exceeds a threshold, then a failure flag is set and a DTC is stored.

Stuck Detection
Stuck at monitoring executes when closed loop fuel pump control is executing. It checks that the fuel rail pressure signal has varied by at least 5 kPa over a range of demanded fuel pump duties. The maximum and minimum fuel rail pressures are updated each time. The change in demand duty is integrated and when the integral reaches 4%, the variation between the maximum and minimum values is checked. If it is less than 5kPa, failure judgment is made; otherwise, a normal judgment is made.

Offset Detection
This part of the monitor executes when the vehicle is idling. When closed loop fuel pump control is executing, a settle timer is incremented. After the counter reaches 5 seconds monitoring can be started. This is to allow the system time to settle after a transition from open to closed loop fuel pump control. Once the counter is greater than 5 seconds the target pressure is checked against the actual fuel rail pressure. If the error is less than the failure threshold, a normal counter is started. If the normal counter reaches 1 second, normal judgment is made. If the target to actual error is greater than the failure threshold, a failure counter is started. If the failure counter reaches 5 seconds then failure judgment is made.