What does it mean?
This is a plausibility fault on fuel pressure sensor A: the signal is electrically valid but does not agree with what the fuel system should be doing. The module commands a pump speed or a regulator duty and expects the measured pressure to follow within a tolerance band and within a defined settling time; it also expects the value to fall when the pump is off and to respond to a change in demand.
When the reading stays flat while pressure should be changing, holds a fixed offset, or reacts far too slowly, the module concludes the value cannot be used for closed loop control. Because pump control is calculated from this feedback, an inaccurate sensor pushes the whole fuel supply pressure away from target without ever setting a circuit code. The fault splits roughly evenly between a drifted sensor and a fuel supply that genuinely cannot hold the commanded pressure.
Symptoms
- MIL (check engine lamp) on, sometimes with reduced power
- Hesitation, surging or a lack of power under acceleration and when towing
- Long cranking, particularly after the vehicle has stood
- Fuel trims drifting away from centre as the injectors deliver more or less than calculated
- Fuel pump running noticeably louder or at a constant speed
- Poor fuel economy without any other obvious fault
Likely causes
- Drifted or contaminated fuel pressure sensor reporting a consistent offset
- Restricted fuel filter or a partially blocked supply line, so the pressure genuinely falls short under demand
- Weak fuel pump or a failing pump control module unable to hold the commanded pressure
- Leaking fuel pressure regulator or a stuck open return, bleeding pressure away
- Air drawn into the supply because of a leaking pickup or a loose fitting
- High resistance in the signal or ground circuit shifting the reported value without leaving the valid range
- Software calibration mismatch after a sensor, pump module or control module replacement
How to fix it
- With the ignition on and the pump off, confirm the sensor reads the correct resting value; an offset with no pressure applied exposes a drifted sensor immediately
- Fit a mechanical gauge to the fuel system test port and compare it against the scan tool value at idle, under load and during a snap throttle
- Graph commanded pump duty against actual pressure; a pump working at maximum while pressure stays low proves a supply problem, not a sensor
- Replace or inspect the fuel filter if it is at or past its service interval, and check the supply line for restrictions and kinks
- Perform a pressure hold test after shutdown to identify a leaking regulator, injector or check valve
- Voltage drop test the signal and ground wires, since a small drop creates exactly the offset the module objects to
- Replace fuel pressure sensor A only when the mechanical gauge proves the real pressure is correct and the sensor still disagrees