Diagnostic Aids
WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
- ECM uses the FTP sensor to detect the amount of vacuum pulled on the EVAP system during the leak diagnostic tests. Ensure that the fuel tank pressure sensor is not skewed by verifying the FTP sensor on the scan tool is 1.30-1.70 volts with the ignition on and the fuel cap removed.
- If this test fails, a warm test will be performed and can only pass, not fail, a diagnostic test. The purpose of this test is to keep the Malfunction Indicator Light (MIL) off during the initial test if the customer starts the vehicle with the fuel cap off.
- Visually inspect for a large leak in the EVAP system. Locate the leak with the OBD II/Enhanced Emissions Testing Equipment (J-41750).
- The following are possible causes of a large leak:
- - Fuel cap is missing, is incorrectly installed or is leaking.
- - EVAP vent solenoid is stuck open.
- - EVAP purge solenoid is stuck closed or is blocked.
- - EVAP vent hose is loose or is damaged.
- - EVAP canister is leaking.
- - Fuel sender assembly O-ring is leaking.
- - Fuel tank or filler neck is leaking.
- - A condition may exist where a leak in the EVAP system only exists under a vacuum condition. By using the scan tool Purge/Seal function to create a vacuum, seal the system and observe the FTP sensor parameter for vacuum decay, this type of leak may be detected.