Evaporative Emissions (EVAP) System, Leak Check

Evaporative Emissions (EVAP) System, Leak Check

Function description
The Evaporative emissions system, including fuel tank, is equipped with self check leak diagnosis.

Diagnosis operates by first pressurizing the system and then measuring leak rate between tank pressurizations. A DTC is generated when the rate is equivalent to a leak caused by a 1 mm diameter hole or larger.

During diagnosis, the Leak Detection Pump (LDP) -V144- builds up a pressure of approx. 30 mbar in the EVAP canister. The pump will switch OFF when preset pressure is reached. When pressure falls below a certain value, the pump will switch ON again. On Board Diagnosis (OBD) monitors and compares time between switched ON periods, and if too short, will store a malfunction in DTC memory.


NOTE:
- Hose connections are secured with either spring or clamp type clips.
- Always replace clips with either clamp-type or spring-type clips.
- Use VAG 1921 pliers when installing spring type clips.