What it means
The mechanical pressure relief valve has activated repeatedly within a short window — pressure regulation is failing more than once.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
The fuel system's mechanical pressure relief valve opens when pressure exceeds its relief threshold, while the control module monitors pressure and relief activity. P018F sets when the valve activates repeatedly within a short period, pointing to recurring overpressure or a pressure signal that incorrectly indicates it.
Common causes
Most likely first.
- Fuel pressure regulator sticking intermittently
- Fuel pressure control valve malfunction
- Fuel pump delivering excessive pressure
- Fuel pressure sensor giving an incorrect reading
Symptoms
- Check engine light on
- Hard starting or rough running
- Loss of power or stalling
- Fuel odor or visible fuel leak
How to diagnose it
- Check freeze-frame data and scan-tool fuel pressure readings for repeated pressure spikes or relief events, and note whether they occur during starting, idle, or load.
- Inspect the fuel system for a fuel odor, wet connections, or visible leaks; do not run the engine if fuel is leaking.
- Compare measured and commanded fuel pressure using the manufacturer's procedure to determine whether pressure is actually rising too high.
- Check the fuel pressure sensor and its wiring for an inaccurate reading that could trigger unnecessary relief activity.
- If pressure is confirmed high, test the pressure regulator, control valve, and pump using the manufacturer's procedures to identify the component causing it.
Common fixes
- Repair any confirmed fuel leak before operating the vehicle.
- Repair wiring or replace the pressure sensor if it falsely reports overpressure.
- Replace or repair a sticking fuel pressure regulator or control valve.
- Repair or replace the fuel pump if testing confirms it is delivering excessive pressure.
Can I keep driving?
Do not drive if you smell fuel, see a leak, or the engine is stalling; shut it off and arrange safe assistance because leaked fuel can ignite. Otherwise, avoid driving under load and address the recurring overpressure promptly, since it can worsen running problems and fuel-system damage.
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.