'Check engine' light can be triggered by escaping fuel vapors

Your car’s “Check Engine” or “Service Engine Soon” light can flash on for more than 1,400 different reasons. The light is part of your vehicle’s on-board diagnostics (OBD) system and can indicate anything from a quick fix like a loose gas cap to a major repair like a catalytic converter. And here’s another example of a problem that can trigger the light…

Trouble code: P0456 Evaporative Emissions System – Small leak detected

The EVAP system is a closed system that captures fuel tank vapors and prevents them from escaping into the atmosphere. When the light comes on for this reason, you most likely won’t notice the car driving any differently. Everything will seem fine, except for the glowing check engine light on the dashboard.

Here are some possible causes:

• Missing or loose fuel cap
• Incorrect fuel cap used
• Evaporative emission canister or fuel tank leaks
• Evaporative emission system hose leaking
• Fuel tank leaking
• A small leak in any of the EVAP hoses or fuel tank hoses
• A small leak in the purge valve or vent valve

Possible solutions

• Check your gas cap and make sure it’s tight and there’s no rust or anything else preventing it from sealing.
• Bring it to Hong Kong Auto Service. We’ll use a smoke machine and watch to see if any smoke is coming out of the system at any EVAP component. If so, that component is the leaky culprit.