P0093 means Fuel System Leak Detected – Large Leak. The computer has seen fuel rail pressure fall faster than it should, or fuel demand far higher than expected, which it interprets as a large leak in the high-pressure fuel system. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0093 means
Modern engines measure boost and fuel rail pressure and compare them with a desired value calculated from engine speed, load and throttle. When actual pressure falls short of desired for long enough, the computer sets a code and often reduces power to protect the engine. Watching desired and actual values side by side on a scan tool shows whether the shortfall is constant or only appears under load.
P0093 symptoms
- Engine stalls or shuts down
- Strong fuel smell
- Loss of power or no start
Common causes of P0093
- External leak at a high-pressure line, fitting or rail
- Internal leak such as a cracked injector body or excessive injector return
- Failed pressure relief valve
- Faulty rail pressure sensor reading
How to diagnose P0093
- Inspect carefully for external fuel leaks with the engine off, never by hand near running high-pressure lines
- Check the oil level for fuel dilution
- Run an injector return-flow test
- Compare rail pressure readings with a known-good sensor
Can you drive with P0093?
No: a large fuel leak is a fire risk and can stall the engine. Have it towed or inspected first.
P0093 tips
Never feel for leaks around running high-pressure fuel lines; a pinhole leak can inject fuel through skin. Inspect with the engine off and use cardboard to detect spray if needed.
Will P0093 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0093 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0087 | Fuel Rail/System Pressure Too Low |
| P0094 | Fuel System Leak Detected – Small Leak |
| P0191 | Fuel Rail Pressure Sensor A Circuit Range/Performance |
Guides that help
- bad diesel injector symptoms
- how to bleed a diesel fuel system
- fuel pump, filter and regulator symptoms
When it is more than a sensor
Our superchargers page lists supercharger kits, and diesel owners can read the 6.7 Cummins turbo guide. If a failed turbo or fuel pump has damaged the engine, compare engines by code on our engines page.
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