What it means
Alt fuel rail pressure sensor signal voltage below expected range. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The alternative fuel rail pressure sensor sends a voltage signal representing pressure in the engine's CNG, LPG, or hydrogen fuel rail. The control module monitors that signal against the circuit's expected electrical range. This code sets when the signal is too low, which can result from a signal wire shorted to ground, a poor connection, or a faulty sensor.
Common causes
Most likely first.
- Signal wire shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check-engine light on
- Alternative-fuel pressure reading may be inaccurate or unavailable
- Poor running or reduced power may occur
How to diagnose it
- Save freeze-frame data and check live scan data for alternative fuel rail pressure, noting whether the reading is unusually low or absent.
- Following the manufacturer's fuel-system safety instructions, inspect the rail pressure sensor connector and harness for corrosion, water entry, loose pins, or chafing.
- Check for a signal wire short to ground, especially where the harness passes near sharp edges or hot components.
- Measure the sensor supply, ground, and signal circuits using the wiring diagram and compare results with the manufacturer's specification.
- If the circuit tests correctly, test the rail pressure sensor and replace it if its output remains low.
Common fixes
- Clean and secure corroded or loose rail sensor connector terminals.
- Repair a signal wire shorted to ground or damaged harness insulation.
- Restore a poor sensor supply or ground connection.
- Replace the rail pressure sensor if it fails the manufacturer's electrical test.
Can I keep driving?
Avoid hard acceleration and limit driving if the engine runs poorly or loses power, since fuel delivery may be affected. Stop and follow the vehicle's fuel-system safety instructions if you suspect a leak or receive a warning requiring shutdown.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.