ASE G1 Auto Maintenance and Light RepairEngine SystemsMedium
A vehicle owner complains of a strong gasoline smell around their vehicle, especially after refueling. There are no visible leaks on the ground or from the fuel lines. A 'Check Engine' light is illuminated with DTC P0442 (Evaporative Emission System Leak Detected - Small Leak). What is the MOST likely cause?
- ALeaking fuel injector
- BClogged fuel filter
- CPunctured fuel tank
- DLoose or faulty fuel cap
Show answer & explanationAnswer & explanation
Correct answer: D. Loose or faulty fuel cap
DTC P0442 specifically points to a 'small leak' in the Evaporative Emission (EVAP) system. The most common and often overlooked cause of a small EVAP leak, especially after refueling, is a loose, damaged, or faulty fuel cap, which prevents the system from sealing properly.
Why the other options are wrong
- A. A leaking fuel injector would cause a gasoline smell in the engine bay and rich running conditions, not typically an EVAP code or a smell associated with refueling.
- B. A clogged fuel filter would primarily affect fuel delivery to the engine and cause performance issues, not an EVAP leak or gasoline smell outside the tank.
- C. A punctured fuel tank would cause a large, visible leak on the ground, not a 'small leak' EVAP code with no visible external leaks.
EVAP System Small Leak (P0442)
A Diagnostic Trouble Code indicating a detected leak in the Evaporative Emission Control System, often caused by a loose fuel cap or a small crack in a vacuum hose.
- Often triggered by a loose, missing, or faulty fuel cap.
- Results in a gasoline smell due to vapor escape.
- The EVAP system captures fuel vapors to prevent release into the atmosphere.
Memory trick: A 'LOOSE CAP' lets 'GAS' vapors 'ESCAPE' and triggers 'P0442'.