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 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 1.4 and 1.6 volts with ignition on and engine off.

Possible cause of a small EVAP leak:

Fuel cap leaking.
EVAP vent solenoid valve not fully seating.
EVAP service port valve leaking.
EVAP line/hose connections leaking.
Primary or secondary fuel sender O-ring leaking.
Fuel tank pressure sensor seal leaking.

For potential leak areas, see Figure .