DTC Descriptor DTC P0455 - Evaporative Emission (EVAP) System Large Leak Detected Circuit/System Description The engine control module (ECM) tests the evaporative emission (EVAP) system for a large leak or restrictions to the purge path in the EVAP system. When the enabling criteria has been met, the ECM commands the EVAP vent solenoid valve and purge solenoid valve ON, allowing vacuum into the EVAP system. The ECM monitors the fuel tank pressure (FTP) sensor voltage to verify that the system is able to reach a predetermined level of vacuum within a set amount of time.
Diagnostic Aids * Inspect for a loose, missing, damaged, or incorrect fuel fill cap. * Inspect for a damaged fuel filler neck seal surface. * A blockage or restriction in the EVAP purge solenoid valve, purge pipe, EVAP canister, or vapor pipe, can cause this DTC to set. * The EVAP system can be filled with smoke more quickly and completely by opening the system opposite the end where the smoke is injected. For example, when injecting smoke at the service port remove the fuel fill cap, or temporarily leave the vent open, until smoke is observed, then close the system and continue testing. If using a fuel cap adapter at the filler neck, use the J 41413-VLV at the service port to allow the system to fill faster. * To help locate intermittent leaks using the GE 41413-A move all EVAP components while observing smoke with the GE 41413-SPT. * Individual components can be isolated and tested using adapters in the J 41413-300. * When servicing the EVAP system, test pressure must not exceed 13 in H20 (0.5 PSI) as pressure in excess of this could cause system components to perform inaccurately. * A condition may exist where a leak in the EVAP system only exists under a vacuum condition. This type of leak may be detected by using the scan tool Purge/Seal function to create a vacuum in the EVAP system and then observe the FTP Sensor parameter for vacuum decay.
what you need to do
1- Change oil & filter , make sure oil clean,
2- inspect the wires to the cam sensor
3- Change the MASS Air flow sensor ( very common failure on malibu )
4- Check vacuum lines for evap system, either vacuum line leaking or bad evap solenoids