What is the P0446 Code?
P0446 is a generic OBD-II powertrain code, which means that it applies to all makes and models of vehicles from 1996 and newer, such as Chevrolet, Toyota, Ford, Honda, Nissan, etc. This code occurs when there is a problem detected with the Evaporative Emission Control (EVAP) System Vent Control Circuit.
What is an EVAP Vent Valve?
What the EVAP System Does The EVAP system captures fuel vapors from the fuel tank and prevents them from escaping into the atmosphere. The vent valve is the most important, because it seals the system when needed. When the key turns on, it receives 12V battery voltage. When it is working properly, the vent valve permits the system to pressurize to detect leaks.
Symptoms of a P0446 Code
This presents a problem because there are not any clear driving symptoms that accompany P0446. However, the Malfunction Indicator Lamp (MIL) or Check Engine Light will turn on.
Common Causes of P0446
The P0446 code can be caused by several factors including:
Stuck or malfunctioning EVAP vent valve – The valve may be stuck closed or malfunctioning.
Wiring – Open, short or excessive resistance in the vent valve control circuit.
Vent valve blockage – Dirt, debris, or spider webs can block vent line.
Faulty Powertrain Control Module (PCM) – Though uncommon, a bad PCM could cause this code.
Charcoal canister failure – If the canister is saturated or cracked, it cannot function.
Vehicles That Commonly Experience P0446
P0446 is a generic trouble code, meaning nearly every make has a version, but some vehicles are particularly prone to P0446, including:
Chevrolet Silverado, Chevy Tahoe, and Chevy Impala – GM trucks and SUVs have a lot of vent valve problems because debris can block the system.
Toyota Camry, Toyota Corolla, and Toyota Tacoma — EVAP vent valve failures are a common ailment in Toyotas, due in part to issues with its solenoid.
Ford F-150: Ford Explorer: Ford Escape: Ford Trucks and SUVs commonly fail due to clogged vent valves or vacuum leaks.
How to Fix a P0446 Code
Here are solutions when your OBD-II scanner reads P0446:
Replace the EVAP Vent Valve
In many cases, replacing a vent valve that is frozen closed or nonfunctioning is the simplest repair. This issue is prevalent in Chevy, Toyota, and Ford cars.
Examine and Fix Wiring Problems
Check for:
Broken or frayed wires.
Shorts in vent valve control circuit.
Excessive resistance in the wiring harness.
Unblock The Vent Valve:
The vent valve sometimes gets clogged with dirt, debris, or spider webs. Cleaning it out with compressed air or replacing it can fix the problem.
Inspect and Swap the Charcoal Canister
P0446 can also get set due to a saturated or cracked canister. If you’re noticing fuel near the canister, you may need to replace it.
Reflashing the PCM (PCM Replacement, If Necessary)
While PCM failure is rare, if everything else is functioning normally, it could be the cause of the problem. The cure would be an update or replacement of the PCM.