P05F1

What it means

The supply relay or driver for the reductant pump is welded or stuck active - the pump runs continuously, even with the engine off, draining the battery and over-pressurising the dosing circuit.

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

• Supply relay welded

  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 P05F1 diagnosis, causes & costs
• How to read check engine light codes
• Is it safe to drive with the light on?