P0093 fault code: large fuel system leak
Plain-language definition
Fuel System Leak Detected - Large Leak
What does it mean?
This code is seen mainly on diesel common rail systems. The engine computer monitors the fuel the pump delivers, the fuel the injectors use and the pressure in the rail, all together. If the pressure drops faster than expected, or the pump has to deliver an unusually large amount of fuel to maintain the pressure, it concludes that there is a leak in the system.
P0093 is stored when the engine computer calculates that this deviation is big enough to point to a large leak. The leak may be somewhere you can see from the outside (a cracked pipe, a loose fitting), or somewhere you can't, such as too much fuel returning from the injectors. And sometimes, without any real leak, the pressure sensor or the control valve can produce the same picture.
The engine may be hard to start, lose power or stall while driving; on some cars the engine computer may stop the engine when it can't maintain the pressure. You may also notice a smell of fuel or wetness in the engine bay.
How serious is it?
It's a Warning-level code, but if there's a real fuel leak, the situation becomes serious. Leaking fuel can make the engine stop, and if it touches hot engine parts it can also create a fire risk.
Severity is a guide; if the warning light is flashing or you notice symptoms while driving, have the car checked at a workshop.
Common general causes
- An external fuel leak from the high-pressure lines, the fittings or the rail
- Worn injectors returning more fuel than normal
- A leaking pressure control or pressure-limiting valve on the rail
- Fuel supply falling short because there is very little fuel left in the tank or the fuel filter is clogged
- A worn high-pressure pump
- The fuel pressure sensor giving wrong readings
The list shows general causes; a workshop finds the actual cause on your car with a check.
Definitions by make
Some manufacturers record the same code under their own wording:
- Fiat
- Rail pressure - high-pressure circuit
Related codes
How does it appear in the 2dakika report?
Fuel System Leak Detected - Large Leak
If the code is read as a confirmed (stored) fault, the report shows it with the "Warning" severity; in pending or past records, codes that don't request the warning light and aren't critical appear as "Info". If the engine computer stored them, the conditions when the fault was recorded (engine temperature, rpm, speed) are shown too.
Read this code with the OBD-X1, and clear it from the app after the repair.
Clearing the code doesn't fix the fault; if the problem persists, the code comes back.