Diagnostic Aids
WARNING: This page is about a different car, the 2002 Saturn LW200, 2002 Saturn L200, and 2002 Saturn L100. However, it is still accessible from the selected car via links, so may be relevant.
PCM 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 SENSOR on scan tool is 2.35-2.85 volts with ignition on and fuel cap removed.
Make a visual inspection for a large leak of EVAP system. Use EVAP pressure/purge diagnostic cart and ultrasonic lead detector to locate large leak.
Possible causes of a large leak:
- Fuel cap missing, incorrectly installed or leading.
- EVAP vent solenoid stuck open.
- EVAP purge solenoid stuck closed or blocked.
- EVAP vent hose loose or damaged.
- EVAP canister leaking.
- Fuel sender assembly "O" ring leaking.
- Fuel tank or filler neck leaking.
A very large leak, such as a missing fuel cap, may be difficult to pick up with the ultrasonic leak detector. For potential leak areas, see Fig 1 .