Circuit/System Description: Notes

The diagnostic strategy for the EVAP system uses a vacuum pump to test for system leaks after the engine is OFF. A unique fuel tank, EVAP canister, and EVAP vacuum leak pump, work together in order to provide enhanced system diagnosis. The vacuum leak pump, the fuel tank pressure (FTP) sensor and the EVAP canister vent valve are all integral parts of one assembly. The assembly is attached directly to the EVAP canister, located near the fuel tank.

After the vehicle has sat with the engine OFF for more than 5 hours and the engine coolant temperature is less than 35°C (95°F), a comprehensive diagnostic is enabled. The complete diagnostic test can take up to 15 minutes to run, with leak detection comprising the largest portion of the test. The DTC P0455 diagnostic detects evaporative emission system leaks as small as 1.0 mm (0.040 in) and the P0456 diagnostic detects leaks as small as 0.51 mm (0.02 in).

The following table illustrates the relationship between the ON and OFF states, and the OPEN or CLOSED states of the EVAP canister purge and vent valves.