DTC P0449: EVAP Vent Solenoid Control Circuit: Description
WARNING: This page is about a different car, the 2001 GMC Savana, 2001 Chevrolet RV Cutaway, 2001 Chevrolet Cutaway, and 2001 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
A voltage is supplied directly to evaporative emission vent valve solenoid. Powertrain Control Module (PCM) controls solenoid by grounding control circuit via an internal switch called a driver. Primary function of driver is to supply ground for controlled component. Each driver has a fault line which PCM monitors. Voltage of control circuit should be low, about zero volts, when PCM commands a component on. Voltage potential of circuit should be high, about battery voltage, when PCM commands control circuit to a component off. If fault detection circuit senses a voltage other than what PCM expects, fault line status changes causing DTC P0449 to set.