Automotive Service Excellence (ASE) A8 Engine PerformanceEmissions Control Systems Diagnosis and RepairMedium
A vehicle is being diagnosed for a 'Check Engine' light and DTC P0442 (Evaporative Emission System Leak Detected - Small Leak). The technician performs a smoke test on the EVAP system. Smoke is observed escaping from the area around the fuel filler neck, specifically from a cracked rubber hose connecting the filler neck to the fuel tank. What is the correct next step?
- AClear the DTCs and advise the customer to monitor
- BReplace the fuel filler neck hose
- CReplace the vent valve
- DReplace the purge valve
Show answer & explanationAnswer & explanation
Correct answer: B. Replace the fuel filler neck hose
DTC P0442 indicates a small EVAP leak. The smoke test identified the exact source of the leak: a cracked rubber hose at the fuel filler neck. The correct next step is to replace the identified faulty component to resolve the leak and clear the DTC.
Why the other options are wrong
- A. Clearing DTCs without addressing the root cause will result in the 'Check Engine' light returning and the vehicle failing emissions tests.
- C. Replacing the vent valve would not address the identified leak at the fuel filler neck hose.
- D. Replacing the purge valve would not address the identified leak at the fuel filler neck hose.
EVAP Small Leak Diagnosis
Locating and repairing minor leaks in the Evaporative Emission Control System, often indicated by DTC P0442.
- Requires a smoke test for accurate leak detection.
- Common leak points include hoses, fuel cap, and canister components.
- Repair involves replacing the identified faulty component.
Memory trick: Smoke finds the crack, fix what you see!