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.

ECM uses fuel tank pressure sensor to detect amount of vacuum pulled on EVAP system during leak diagnostic tests. Ensure fuel pressure sensor is not skewed by verifying FUEL TANK PRESS. SENSOR on scan tool is 1.3-1.6 volts with ignition on and fuel cap removed.

Use EVAP system tester to locate a small leak.

Possible causes of a small leak:

Fuel cap leaking.
EVAP vent solenoid valve not seating correctly.
EVAP vent hose loose or damaged.
EVAP canister leaking.
Fuel sender assembly "O" ring leaking.
Fuel tank or filler neck leaking.

Small leak diagnostic can only detect a leak more than 0.04" diameter. For potential leak areas, see Figure .