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Home >> Chevrolet >> 2021 >> Blazer RS, FWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 9 (Engine Controls And Fuel - 2.5L (LCV) - Diagnostic Information And Procedures (1 Of 2)) >> Diagnostic Information and Procedures >> DTC P0442 or P0455 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.

For an overview of the component/system, refer to: Evaporative Emission Control System Description

P0442 

This diagnostic tests the Evaporative Emission (EVAP) System for a small leak when the ignition is off and the Conditions for Running the DTC are met. When the ignition is turned off and the EVAP system is sealed, a change in the fuel tank vapor temperature occurs which results in a corresponding pressure change in the fuel tank vapor space. This change is monitored by the control module using the fuel tank pressure (FTP) sensor. With a leak in the system, the amount of pressure change will be less than that of a sealed system.

P0455 

This diagnostic tests the Evaporative Emission (EVAP) System for a large leak or restrictions to the purge path in the EVAP system. When the Conditions for Running the DTC are met the control module commands the EVAP canister vent solenoid valve and EVAP purge solenoid valve on, allowing vacuum into the EVAP system. The control module monitors the fuel tank pressure (FTP) sensor voltage to verify that the system is able to reach a predetermined level of vacuum before a calibrated amount of purge volume has passed through the system.

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