The OBD2 code P0446 on your Chevy indicates a problem with the Evaporative Emission Control (EVAP) system, specifically the vent valve control circuit. This code signifies an improper voltage drop in the vent valve circuit, meaning there’s either too much or too little electrical resistance.
The EVAP system prevents fuel vapors from escaping into the atmosphere. The vent valve, controlled by the Powertrain Control Module (PCM), regulates the flow of air into the EVAP system. When the PCM detects an incorrect voltage signal from the vent valve circuit, it sets the P0446 code.
The PCM supplies 12 volts to the vent valve through a fuse. It monitors the voltage returning through the valve’s electromagnet coil when the valve is inactive. A voltage reading that’s too low, or absent altogether, triggers the P0446 code. Caution: Directly applying 12 volts to the trigger wire can damage the PCM driver. A resistor, like the valve coil or a test light, is necessary to limit current flow. A simple test lamp using a 168 bulb and Metripak 150 terminals can be used for diagnostics.
Common causes of P0446 include a faulty vent valve or a problem within the electrical connection. Corrosion within the connector terminals is a frequent culprit. If corrosion is the issue, a repair pigtail connector can be soldered and sealed with adhesive-lined heatshrink to the existing wiring. Alternatively, replacing the damaged connector with new female Metripak terminals, wire seals, and a connector shell is a viable solution.
The GM part number 15759044 often corresponds to a rectangular vent valve. However, other shapes and manufacturers exist. For instance, a round Echlin vent valve, potentially made in the USA, might be available at NAPA for certain models like the 2005 Silverado. Always confirm compatibility with your specific Chevy model year. Addressing the P0446 code promptly ensures proper EVAP system function, contributing to emissions control and optimal vehicle performance.
