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Generic light-duty diesel DTC / Fuel delivery

P0093: Fuel System Leak Detected — Large Leak

Generic definition: Fuel System Leak Detected — Large Leak

The controller detected a fuel-system condition it interprets as a large leak. This monitor does not locate a leak or prove an external line has failed; pressure loss, a control issue, or a system-specific fault may be involved.

Generic definition
P0087
P0088
P0191

Likely cause paths · unconfirmed

A possible external fuel leak

A line, fitting, filter housing, or other component may leak, but only inspection can locate it.

  • Record where visible wetness appears without approaching or touching it.
  • Note odor, smoke, or stalling and stop use if any leak is suspected.

A possible internal pressure loss or monitoring fault

A system-specific pressure-control, return, or sensor fault can trigger a leak-monitor result without an obvious external leak.

  • Save related codes and freeze-frame data.
  • Tell the technician whether the symptom occurs during cranking, idle, or load.

This generic definition does not distinguish external leakage from the vehicle’s monitor strategy. Safety takes priority over further inspection.

Conditional repair directions

A code is not a parts recommendation. Follow a direction only after the listed evidence confirms its cause.

If confirmed: A possible external fuel leak

Do not drive with a confirmed fuel leak. Have the leaking component repaired and the system checked for safe operation using OEM procedures.

Evidence to confirm

  • A technician locates the leak with the specified inspection or test.
  • The repair is verified with the OEM leak-check procedure.

If confirmed: A possible internal pressure loss or monitoring fault

If no external leak is found, diagnose pressure control and monitoring with the vehicle-specific test sequence before replacing parts.

Evidence to confirm

  • The specified tests isolate pressure loss, regulation, or a sensor/circuit fault.
  • The leak-monitor condition does not recur after repair and verification.

Ordered evidence checks

  1. 01

    Check for immediate fuel hazards

    From a safe position, note any visible liquid or strong fuel odor. If present, do not continue checking or restart the engine.

  2. 02

    Save codes and warning details

    If there is no leak or strong odor, record exact code status, related codes, and scan data before clearing anything.

  3. 03

    Note recent service

    Record recent filter, injector, or fuel-system work for the technician. Do not touch or retighten fittings.

  4. 04

    Locate the loss with the OEM procedure

    Qualified technician / OEM procedure

    A qualified diesel technician must use the vehicle-specific leak and pressure test. Common-rail connections must not be loosened for diagnosis.

Possible symptoms

  • Stalling or no start
  • Fuel odor or visible wetness
  • Reduced power or a warning lamp

The DTC definition is generic; the app’s cause paths are unverified, do not establish a failed part, and are not OEM procedures. Confirm vehicle-specific tests with the maker’s service information or a qualified technician.