What does it mean?
Here the fuel pressure sensor A signal is sitting at or above the highest voltage the module accepts as valid. A working sensor never reaches the top of its 5-volt range in normal service because the fuel system operates well below the sensor full scale value, so a signal pinned at the ceiling is treated as a circuit failure.
An open in the signal wire, the sensor ground or the sensor element itself lets the module internal pull-up drag the input to reference voltage, which is exactly this signature. The module stores the code once the condition persists, discards the reading and controls the fuel pump on a default value, which can leave supply pressure well away from what the engine needs.
A genuinely over-pressurised fuel system is possible but far less common, and it normally comes with regulator or return line complaints.
Symptoms
- MIL (check engine lamp) on, sometimes with reduced power
- Rich running, black smoke or a strong exhaust smell if the module acts on a false high pressure
- Rough idle, hesitation and poor throttle response
- Fuel pump running at a reduced default output, causing a lack of power under load
- Long cranking or difficulty starting
- Fuel odour or a wet return line if pressure really is too high
Likely causes
- Open circuit in the sensor signal wire or its ground return
- Connector unplugged, unlatched or with a corroded, backed-out terminal
- Internally failed sensor stuck at maximum output
- Signal wire shorted to the 5-volt reference or to battery voltage from an adjacent circuit
- Harness damage under the vehicle or in the engine bay after previous work
- Blocked fuel return or a stuck regulator producing genuinely excessive supply pressure
- Control module input circuit failure, the least likely cause
How to fix it
- Read live fuel pressure with the ignition on and the system unpressurised; a value at full scale with no pressure applied confirms an electrical fault
- Inspect the connector for corroded, spread or backed-out terminals, a broken lock and water intrusion
- With the sensor unplugged and the ignition on, jumper the signal pin to ground at the harness connector. A reading that drops to zero proves the wiring and module are good
- If the value stays high with the pin grounded, test the signal wire for an open and for a short to the 5-volt reference or battery positive
- Check the sensor ground for continuity and voltage drop back to its termination
- Where the wiring is sound, verify actual fuel pressure with a mechanical gauge before assuming the sensor is wrong, since a blocked return can create real over-pressure
- Repair the open or short, or replace fuel pressure sensor A, then clear the code and confirm the reading follows pump operation