P04AF

What it means

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.

Is it safe to drive?

The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical.

Most likely causes

• Valve stuck closed

  high

  One of the most commonly reported causes for this code — check this first.

• Carbon or debris buildup preventing free movement

  low

  Less common, but worth ruling out after the more likely causes.

• Component wear with age - mechanical play

  low

  Less common, but worth ruling out after the more likely causes.

Related help

• Full P04AF diagnosis, causes & costs
• How to read check engine light codes
• Is it safe to drive with the light on?