P0446 Evaporative Emmission Control System Vent Control Circuit

OBD-II Trouble Code Technical Description

Evaporative Emission Control System Vent Control Circuit

What does that mean?

This indicates that a part of the EVAP control system is no longer fuctioning correctly. The P0446 code is similar in nature to the P0441 code. The EVAP system consists of many parts, including (but not limited to) the gas cap, fuel lines, carbon canister, purge valve, and other hoses. The (EVAP) emission control system prevents the escape of fuel vapors from a vehicle's fuel system. Fuel vapors are routed by hoses to a charcoal canister for storage. Later, when the engine is running a purge control valve opens allowing intake vacuum to siphon the fuel vapors into the engine.

EVAP emission canister purge is contolled by a valve which allows engine vacuum to pull stored fuel vapors from fuel tank into the engine to be burned, rather than be vented to atmosphere. A vacuum switch is used to detect when flow exists. If the PCM commands purge and sees that the switch is closed (indicating no detected purge flow) P0446 is set.

When the vapor pressure rises to a specified point, the ECM opens the VSV for canister closed valve. Pressure will increase rapidly because of the air allowed into the system. No increase or an increase below specified rate of pressure increase indicates a restriction on the air inlet side. The ECM closes the VSV for pressure switching valve. This action blocks air entering the fuel tank side of system. The pressure rise on the fuel tank side is no longer as great. If there was no change in pressure, the ECM will conclude the VSV for pressure switching valve did not close.

Symptoms

Likely, no symptoms will be discernible to the driver, other than the illuminated Check Engine Light.

Causes

A code P0446 could mean one or more of the following has happened:

• Bad vacuum switch
• Broken or damaged EVAP line or canister
• Open in PCM purge command circuit
• Open or short in Voltage feed circuit to Purge Solenoid
• Faulty purge solenoid
• Restriction in EVAP solenoid, line or canister
• Corrosion or resistance in purge connector
• Bad PCM

Possible Solutions

With a P0446 OBD-II trouble code, diagnosis can be tricky at times. Here are some things to try:

• Common Chrysler fix - Replace Leak Detection Pump / LDP
• Repair damaged EVAP lines or canister
• Repair open or short in voltage feed circuit to Purge Solenoid
• Repair open in PCM purge command circuit
• Replace purge Solenoid
• Replace vacuum switch
• Repair restriction in Evap line or canister or soleniod
• Repair resistance in purge connector
• Replace PCM

Need more help?

If you still need help regarding the P0446 trouble code, please post your concern in the forums.

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