P0446 Code - Evaporative Emission Control System Vent Control Circuit Malfunction

What Does P0446 Mean?

The P0446 code is triggered by the ECU when a malfunction occurs with the EVAP control system vent control valve. The ECU controls this valve as part of the EVAP control system and when the a fault is detected a Check Engine Light appears on the dashboard

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What are the common causes of P0446 ?

• Loose Gas Cap or Refueling While Running – This is, by far, the most common problem encountered by the EVAP system. During refueling, the engine should not be running. The key can be in the OFF or ACC positions, but should not be in the ON or RUN positions. When refueling is completed, the gas cap should be reinstalled and torqued properly. Usually, this requires one or three clicks for proper sealing.
• Improper Gas Cap – Some aftermarket gas caps may physically fit, but may be incorrectly vented for your particular vehicle, which may also cause the MIL to illuminate and EVAP system DTCs to be stored. In this case, a new OEM (original equipment manufacturer) gas cap will solve the problem.
• Old Gas Cap or Other Damage – Poor sealing anywhere in the EVAP system can cause problems with EVAP function and monitoring. Be sure to check tubes, hoses, gas cap gasket, fuel fill tube, and charcoal canister for damage or cracks.
• General Motors – A number of TSBs (technical service bulletins) have been released addressing issues with clogged EVAP vents, usually vehicles operated in dusty and dirty environments. Relocating the vent hose to a cleaner or more protected location generally fixes the problem, though you may be able to get away with cleaning it yourself.
• Spiders – It seems that certain arachnids have a penchant for fuel vapors, even the few that escape the canister vent control valve. Building their nests in the vent line blocks the flow, some of them so bad that they cause EVAP DTCs to be set, including P0446, and some so bad that they’ve caused canisters and fuel tanks to crack. Mazda vehicles are notorious for this, resulting in multiple recalls and TSBs, but other vehicles have been found to suffer similar problems, such those made by Honda / Acura and Hyundai / Kia – all vehicles should be suspect, really.

How do you troubleshoot P0446 ?

The original multi-displacement system turned off opposite pairs of cylinders, allowing the engine to have three different configurations and displacements. P0446 code had an elaborate diagnostics procedure, including showing engine trouble codes on the air conditionning display. However, the system was troublesome, misunderstood by customers, and a rash of unpredictable failures led to the technology being quickly retired.

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