What it means
The control module monitors the alternative fuel rail pressure sensor circuit. It sets this code when it detects an electrical fault in that circuit, such as a signal outside the expected electrical range.
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 measures pressure in the fuel rail supplying the engine from a CNG, LPG, or hydrogen system. The control module monitors the sensor circuit for electrical faults that can make rail pressure data unreliable. This code indicates a circuit fault but does not specify a low or high signal.
Common causes
Most likely first.
- Pressure sensor failure
- Open or short in sensor wiring
- Loose, damaged, or corroded connector
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 scan-tool data for alternative fuel rail pressure, noting whether the reading is missing or implausible.
- Following the manufacturer's fuel-system safety instructions, inspect the rail pressure sensor connector and harness for looseness, corrosion, heat damage, or chafing.
- Check the sensor circuit for opens and shorts using the vehicle wiring diagram and manufacturer's procedure.
- Measure the sensor supply, ground, and signal circuits and compare results with the manufacturer's specification.
- If the circuit tests correctly, test the rail pressure sensor and replace it if its output is faulty.
Common fixes
- Secure a loose connector or clean corroded terminals at the rail pressure sensor.
- Repair damaged or shorted rail pressure sensor wiring.
- Restore a poor sensor supply or ground connection.
- Replace a faulty alternative fuel rail pressure sensor.
Can I keep driving?
Limit driving if the engine runs poorly or power drops, since inaccurate rail pressure data can affect fuel delivery. 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.