43.2.1 Monitoring Function
The high pressure fuel control system diagnostic consists of a rationality monitor and an analysis of the difference between the measured fuel pressure value and the set-point fuel pressure value. The diagnosis determines whether the FRP set-point value can be adjusted by the high pressure fuel control.
A non-adjustable FRP which is too high is detected when the measured fuel pressure value exceeds the desired set-point fuel pressure value and the difference between these two values (measured - set-point) is positive. When this positive difference exceeds the calibrated threshold value a calibrated number of times (error counter) for a calibrated period of time, a malfunction is detected and the DTC P302A is set.
A non-adjustable FRP which is too low is detected when the measured fuel pressure value is below the desired set-point fuel pressure value and the difference between these two values is negative. When the negative difference falls below a calibrated threshold a calibrated number of times (error counter) for a calibrated period of time for, a malfunction is detected and the DTC P302C is set.