Diagnostic Aids

If DTC P0440, P0442, P0446 or P0455 is set, EVAP special functions on the scan tool will not be allowed. Clear DTCs before performing these tests.
The ECM uses the FTP sensor to detect the vapor in the fuel tank during all parts of the EVAP diagnostic system test. Make sure the FTP sensor is not skewed by verifying FTP SENSOR on the scan tool is 2.35-2.85 volts with the ignition ON and the engine OFF.
Possible causes of a blocked EVAP vent system:
1. The EVAP vent solenoid has a blocked or stuck valve.
2. The EVAP vent hose from the EVAP canister to the EVAP vent line or the EVAP hose at the EVAP vent box is kinked or pinched.
3. The EVAP canister is restricted.
4. An intermittent condition could be caused by a damaged EVAP vent housing, a temporary blockage at the EVAP vent solenoid inlet, or a pinched vent hose. A blockage in the vent system will also cause a poor fuel fill problem.
5. For intermittent conditions, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.
6. If an EVAP diagnostic test is aborted due to changing enabled criteria, the ECM will run the entire EVAP test up to 3 times per ignition cycle.