What it means
The control module checks whether the alternative fuel rail pressure sensor reading is plausible under current operating conditions. It sets this code when the reading is outside the expected range or does not respond as expected.
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 checks whether the reported pressure is plausible for current operating conditions and changes as expected. This code sets when the reading is out of range or does not respond plausibly, even if the circuit is electrically intact.
Common causes
Most likely first.
- Sensor reading drifted
- Sensor element aged beyond calibration window
- Sensor element contaminated by oil, soot or coolant
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 compare alternative fuel rail pressure scan data with engine operating conditions and the manufacturer's specification.
- Following the manufacturer's fuel-system safety instructions, inspect the rail pressure sensor and connector for damage or contamination.
- Check the sensor wiring and connector for looseness, corrosion, heat damage, or chafing that could distort the reading.
- Compare the reported pressure with an independent pressure check only if the manufacturer's procedure allows it.
- If the wiring is sound and the reading remains implausible, test and replace the rail pressure sensor if it fails the manufacturer's procedure.
Common fixes
- Clean and secure a loose or contaminated sensor connector.
- Repair damaged rail pressure sensor wiring.
- Replace a drifted or faulty alternative fuel rail pressure sensor.
- Clear the code and verify the reading follows operating conditions.
Can I keep driving?
Limit driving if the engine runs poorly or power drops, as 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.