Diagnostic Aids
WARNING: This page is about a different car, the 2002 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
If DTC P0440, P0442, P0446 or P0496 is set, EVAP special functions on scan tool will not be allowed. Clear DTCs before performing these tests.
The ECM uses the fuel tank pressure sensor to detect the pressure of fuel vapor in the fuel tank during all parts of the EVAP diagnostic system test. Ensure the fuel tank pressure sensor is not skewed by verifying fuel tank pressure sensor on scan tool is between 1.40 and 1.60 volts with ignition on, engine off and fuel cap removed.
Make a visual inspection for a large leak of the EVAP system.
Possible causes of a large EVAP leak:
- Fuel cap missing, incorrectly installed or leaking.
- EVAP vent solenoid valve stuck open.
- EVAP purge solenoid stuck closed/blocked or lack of manifold vacuum to solenoid.
- EVAP line/hose connections disconnected/leaking.
- Primary or secondary fuel sender O-ring leaking.
- Fuel tank pressure sensor seal leaking.
- EVAP canister blocked between the EVAP canister purge and tank ports (air should flow each way between the purge and tank ports at the EVAP canister).
To locate possible leak areas, see Fig 1 .