DTC P0442: EVAP System - Small Leak: Description

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2003 GMC Sonoma, 2003 GMC Safari, 2003 GMC Jimmy, 2003 Chevrolet S10 Pickup, and 2003 Chevrolet Blazer. However, it is still accessible from the selected car via links, so may be relevant.

This diagnostic tests the Evaporative Emission (EVAP) system for a small leak when the key is turned OFF and the correct conditions are met. Heat is transferred into a vehicle fuel tank while the vehicle is operating. When engine is turned OFF, a change in the fuel tank vapor temperature occurs, which results in corresponding pressure changes in the fuel tank vapor space. This change is monitored by the control module using the fuel tank pressure sensor input. The control module then makes a judgement on the integrity of the system. With a 0.020" (0.51 mm) leak in the system, the amount of pressure change observed is significantly less than that of a sealed system. If the control module detects a pressure change less than a calibrated amount, DTC P0442 sets.