Generic OBD DTC

Ford P0455: EVAP System Gross Leak Detected

The evaporative emissions system reported a gross leak condition — separate from P1000 incomplete-readiness status.

Handheld scan tool on a car seat connected for an OBD readiness check

Moderate — diagnose the related faultEVAP

What the code tells you

The PCM detected an EVAP gross-leak condition under that test’s criteria.

What it does not tell you

That a loose cap is always the cause.
That P1000 is an EVAP leak code.

Diagnostic direction

1
If EVAP is the monitor that will not complete, look for EVAP DTCs such as P0455/P0442/P0456.
2
Fuel-level and temperature windows still matter for EVAP testing even after a leak is repaired.

Related codes

P1000, P0442, P0456

Possible causes are listed only when they are this code’s actual meaning — not a generic template pasted onto every DTC.

This site provides general diagnostic information. Vehicle procedures vary by model, year, engine, and calibration. Follow Ford service information and local regulations, and use a qualified technician when diagnosis or repair exceeds your experience.