P0456low severityPowertrain
EVAP System Leak Detected (Very Small Leak)
on 2007 Audi Q7 4.2L V8 · AWD
What this code means
A very small leak has been detected in the EVAP system. These are the hardest EVAP leaks to find.
Symptoms
- Check Engine Light
- Very slight fuel smell possible
Common causes
- Gas cap seal worn
- Micro-crack in EVAP hose
- O-ring deterioration
- Charcoal canister hairline crack
- Fuel tank seal degradation
Diagnostic steps
- Check and replace gas cap first
- Smoke test EVAP system at low pressure
- Inspect all hose connections
- Check canister and all seals
- May need to pressurize fuel tank
Repair notes
Replace gas cap first. If code returns, smoke test is essential. Very small leaks can be time-consuming to locate.
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