P0401

What it means

This means the system that recirculates exhaust gases back into the engine to reduce emissions isn't working properly, usually because it's clogged with carbon.

Is it safe to drive?

While you can typically drive with a P0401 code, prolonged driving can lead to increased engine temperatures, potential engine damage from knocking, and higher emissions. It's best to address it soon.

Most likely causes

• Clogged EGR valve or passages

  high

  Carbon buildup is the most common cause, restricting the flow of exhaust gas.

• Faulty EGR valve

  medium

  The valve itself may be stuck closed or not opening sufficiently due to internal failure.

• Faulty EGR solenoid or sensor

  medium

  These components control or monitor the EGR valve's operation; a failure can prevent proper flow.

• Vacuum leak affecting EGR operation

  low

  Some EGR systems rely on vacuum; a leak can prevent the valve from opening.

Related help

• Full P0401 diagnosis, causes & costs
• How to read check engine light codes
• Is it safe to drive with the light on?