What does it mean?
This code reports that the signal from fuel pressure sensor A has fallen below the lowest voltage the module treats as valid. The sensor is supplied with a 5-volt reference and produces an offset voltage even with no pressure in the system, so a reading close to zero is electrically impossible for a healthy circuit and cannot simply mean an empty fuel line.
The module compares the signal against a fixed low threshold, requires the condition to persist for a calibrated time, then stores the code and stops using the value to control fuel pump output. It will normally command a default pump duty, which can leave pressure either too high or too low for the actual demand. The key diagnostic question is whether the circuit is shorted or the system has genuinely lost fuel pressure, because both produce similar driving complaints.
Symptoms
- MIL (check engine lamp) on, often with reduced power
- Extended cranking, hard starting or a no-start
- Hesitation, stumbling or a stall under load
- Fuel pump running at a fixed default speed rather than varying with demand
- Lean running codes appearing alongside the pressure fault when supply is genuinely low
- Fuel smell or a visible leak if a mechanical failure is contributing
Likely causes
- Signal wire shorted to ground, often where the underbody or engine bay harness is chafed
- Loss of the 5-volt reference to the sensor, which pulls the output to zero
- Water, corrosion or fuel contamination inside the sensor connector bridging the signal to ground
- Internally failed sensor with a shorted output
- Melted or damaged insulation where the harness passes close to the exhaust
- Genuine loss of fuel supply pressure caused by a failed pump, a blocked filter or a large leak
- Control module reference or input circuit failure, which is uncommon
How to fix it
- Read the live fuel pressure value with the ignition on and the pump running; a value at zero while the pump is clearly working confirms a circuit fault
- Unplug the sensor and watch the scan tool. A jump to full scale means the wiring is intact and the sensor is shorted; a value that stays at zero means the signal wire is grounded
- With the sensor unplugged and the ignition on, measure the 5-volt reference and the ground at the harness connector
- Test the signal wire for a short to ground with the harness disconnected from the module, following it along heat sources and chafe points
- Confirm actual fuel pressure with a mechanical gauge before condemning anything electrical
- Repair the shorted conductor or connector, protect and re-route the harness, then clear the code
- Replace fuel pressure sensor A once reference, ground and signal circuits have all been proven good