Circuit Description
The Evaporative (EVAP) emission system includes the following components:
- Fuel tank
- EVAP emission vent solenoid
- Fuel tank pressure sensor
- Fuel pipes and hoses
- Fuel vapor lines
- Fuel cap
- EVAP emission canister
- Purge lines
- EVAP emission canister purge valve
- EVAP emission service port
The EVAP emission system is checked by applying vacuum to the EVAP emission system and monitoring for a vacuum decay. The Engine Control Module (ECM) monitors the vacuum level through the fuel tank pressure sensor signal.
At the appropriate time, the EVAP emission canister purge valve and the EVAP emission vent solenoid are turned ON, allowing the engine to draw a small vacuum on the entire evaporative emission system. After the desired vacuum level has been achieved, the EVAP emission canister purge valve is turned OFF, sealing the system. If a sufficient vacuum level cannot be achieved, a large leak is indicated. This can be caused by the following conditions:
- Missing or faulty fuel cap
- Disconnected or faulty fuel tank pressure sensor
- Disconnected, damaged, pinched or blocked EVAP emission purge line
- Disconnected or faulty EVAP emission canister purge valve
- Disconnected or faulty EVAP emission vent solenoid
- Open ignition feed circuit to the EVAP emission vent or purge solenoid
- Damaged EVAP emission canister
- Leaking fuel sender assembly O-ring
- Leaking fuel tank or fuel filler beck
Any of the above conditions can set DTC P0455.
The test is failed if the tank vacuum is less than 2.5 kPa and the manifold vacuum integral is greater than predetermined value (proportional to purge mass from the tank) for cold test. And the test is failed if the tank vacuum is less than 10 in. H2O during PRESET mode and manifold vacuum integral is greater than 2, 400 cts (proportional to purge mass from the tank) for preset test.