P20A6

What it means

The drive circuit for the air-assist pressure-control valve in the DEF system is open — atomisation pressure cannot be regulated, dosing accuracy degrades.

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

• Solenoid winding open

  high

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

• Pin pushed back out of connector body

  low

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

• Cracked solder joint inside the module or sensor

  low

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

Related help

• Full P20A6 diagnosis, causes & costs
• How to read check engine light codes
• Is it safe to drive with the light on?