The emissions system function is to lower raw fuel vapor release into earths atmosphere and to lower pollutants from exhaust system emissions. The system has specially calibrated fuel caps that must seal properly and allow the flow of air in only one direction under certain conditions on many vehicles. Other typical components are vent valves, charcoal canister, leak detection devices, recirculation valve, air pumps, purge valve, and catalytic converters. The emissions system is responsible for many service engine soon light illuminations.
- diagnose fault codes.
- check integrity of hoses and connections.
- check fuel cap sealing.
- function test each system component.