What it means
The control module monitors the alternative fuel high-pressure system for pressure loss consistent with a small leak. It sets this code when detected leakage exceeds the system’s calibrated threshold while conditions allow the leak monitor to run.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The alternative-fuel high-pressure system supplies fuel at elevated pressure, and the control module monitors pressure behavior for evidence of leakage. This code sets when pressure loss fits the system’s small-leak criteria while the monitor can run; an aged seal or loose high-pressure fitting can let fuel escape.
Common causes
Most likely first.
- Seal aged at fitting or valve
- High-pressure fitting loose
Symptoms
- Check-engine or alternative-fuel system warning light, if equipped
- Fuel odor, if the leak is externally detectable
- Reduced power or poor acceleration
How to diagnose it
- Review freeze-frame data and alternative-fuel pressure data to see when the leak monitor detected pressure loss.
- With the system in the safe state specified by the manufacturer, inspect accessible high-pressure fittings and valve seals for signs of leakage.
- Check for fuel odor around the vehicle and fuel-system components without touching or loosening high-pressure parts.
- Have suspected high-pressure joints checked using the manufacturer’s leak-detection procedure and equipment.
- If no external leak is found, compare pressure decay and sensor data with the manufacturer’s specification to determine whether the issue is a seal, fitting, or monitoring fault.
Common fixes
- Replace a degraded seal at the leaking fitting or valve using the approved procedure.
- Tighten or repair a loose high-pressure fitting to the manufacturer’s specification.
- Replace a damaged fitting or valve if it cannot seal correctly.
- Clear the code and verify that the system holds pressure under the specified test conditions.
Can I keep driving?
Treat any fuel odor or suspected high-pressure leak as urgent: stop driving, keep ignition sources away, and arrange safe inspection because escaping fuel can create a fire hazard. Even a small leak can worsen and reduce power.
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.