P0093: Fuel System Leak Detected – Large Leak
The fuel pressure drops so quickly that the engine control unit suspects a large leak.
High risk
Stop and check. A fuel leak is a fire risk.
Short answer · Can I keep driving with P0093?
No, not until it is checked. Look under the car and around the engine for fuel and smell for diesel or petrol. If you find a leak, do not start the engine and have the car towed.
What does P0093 mean?
P0093 is mostly set on diesel and direct-injection engines. The engine control unit compares the fuel it delivers with the pressure it sees in the rail; if pressure falls much faster than injection explains, it assumes fuel is escaping. A leaking high-pressure line or fitting, an injector leaking back too much fuel, a faulty pressure control valve or a faulty rail pressure sensor are typical causes. Running out of fuel can also set it.
What the car does when the code is set
The check engine light comes on and many engines limit power to protect themselves. The car may hesitate under acceleration, misfire or stall, especially under load, and it may be hard to restart.
How the system works
A low-pressure pump in the tank supplies fuel to the engine. On port-injection petrol engines that pressure feeds the injectors directly. On diesels and direct-injection petrol engines, a mechanical high-pressure pump raises it much further, into a common rail that feeds all the injectors. A pressure sensor on the rail tells the engine control unit the actual pressure, and a regulator or metering valve adjusts it to the target. If the measured pressure stays below the target for too long, the control unit stores a low-pressure code and may limit power.
Common symptoms
Possible causes
Listed without ranking. The cause on your car depends on make, engine and mileage — see the maker notes below.
- Clogged fuel filterRestricts flow, especially under load.
- Weak fuel pumpThe in-tank pump or high-pressure pump cannot keep up.
- Faulty pressure sensor or regulatorThe pressure is measured or controlled incorrectly.
- Air in the fuel system or running low on fuelCommon on diesels after running the tank dry or after a filter change.
- Fuel leakAn external leak lowers the pressure.
How it is diagnosed
- Check fuel level and leaksMake sure there is enough fuel and look for wet spots or fuel smell under the car and in the engine bay.
- Compare desired and actual pressureLive data shows the target and measured rail pressure. A gap under load points to supply problems.
- Check the filter and low-pressure supplyReplace an old filter and measure the feed pressure from the tank pump.
- Test the pressure sensorCompare the sensor reading with a mechanical gauge where possible.High-pressure fuel systems can hold pressure after switching off. Only a trained technician should open them.
Questions about P0093
Is P0093 always a real leak?
Not always. Injector leak-back and a faulty pressure valve or sensor can look like a leak. But because fuel leaks can cause fires, rule out an external leak first.
Why does the engine lose power only under load?
Under load the engine needs the most fuel. A weak pump or clogged filter can keep up at idle but not under full load.
Can I drive until the next service?
Not recommended. The engine may stall in traffic. Have the fuel filter and pressure checked soon.