P04AF

EVAP System Purge Control Valve B Stuck Closed

Moderate severity

Same as P04AE but the valve B is stuck closed - no vapor purge possible through this stage, leading to elevated tank pressure and possible canister saturation.

Common causes

Valve stuck closed
One of the most commonly reported causes for this code — check this first.
high
Typical part cost: $130-390
Carbon or debris buildup preventing free movement
Less common, but worth ruling out after the more likely causes.
low
Typical part cost: $130-390
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First things to check

1Confirm the code with a scan tool and check for additional related codes.
2Inspect the relevant sensors, wiring, and connectors for damage or corrosion.

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Related codes

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Frequently asked questions

What does P04AF mean?

P04AF means "EVAP System Purge Control Valve B Stuck Closed". It is a generic OBD-II code that points to a fault in the auxiliary emission controls.

What are the most common causes of P04AF?

valve stuck closed; carbon or debris buildup preventing free movement; component wear with age - mechanical play — these are the most commonly reported causes. Verify with a proper diagnosis before replacing parts, or use the Wrenchify app for a vehicle-specific diagnosis.

Can I keep driving with this code?

The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical. Use the Wrenchify app for a full diagnosis specific to your vehicle.

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