Evaporative Emission System Leak Detected (Small Leak)
Common Symptoms
- Check engine light on
- Faint fuel smell possible
- No drivability symptoms
- May fail emissions test
Most Likely Root Causes
- Slightly loose fuel cap
- Small crack in EVAP hose or fitting
- Faulty purge valve with small leak
- Pinhole leak in charcoal canister
- Leaking fuel tank pressure sensor
Full step-by-step tests, DVOM guidance, and pinout data are available inside the AI Diesel Tech diagnostic session.
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Severity / Derate Risk
Low — no drivability impact.
Component Location
Same EVAP system as P0455. Small leaks often at hose connections, fuel cap seal, or purge valve.
Manufacturer Notes
Small leaks are harder to find than large leaks. Smoke machine is the most reliable diagnostic tool. Check all hose clamps and connections.
Also diagnosing J1939 SPN/FMI codes?
Heavy-duty trucks often throw both OBD-II and J1939 faults simultaneously. AI Diesel Tech handles both protocols in a single guided session.
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