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.

If DTCs P0440, P0442, P0445 or P0446 is set, EVAP special functions on the scan tool will not be allowed. Clear DTCs before performing these tests.
The ECM uses the FTP sensor to detect the vapor in the fuel tank during all parts of the EVAP diagnostic system test. Ensure the FTP sensor is not skewed by verifying FTP sensor on the scan tool is 1.30-1.70 volts with the ignition on and engine off.
The most likely cause of DTC P0440 is a stuck open EVAP purge solenoid. Command the EVAP Purge Solenoid ON at 70 percent duty cycle with the scan tool. The solenoid should click at an even rate. Replace solenoid if it intermittently sticks.