OBD-II code · Powertrain (generic)
P05F1 Reductant Pump Supply Voltage Circuit Stuck On
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 with P05F1?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelySupply relay welded
- Less likelyCarbon or debris buildup preventing free movement
- Less likelyComponent wear with age - mechanical play
Symptoms
- Check engine light or NOx warning on
- AdBlue/DEF level or quality warning
- Possible no-start countdown after ignore period
- Failed emissions inspection (NOx)
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.6–2 h
- Emissions test
- Likely to fail
- Parts involved
- Reductant Pump Supply Relay
Related codes
- P05EEReductant Pump Supply Voltage Circuit Open
- P05EFReductant Pump Supply Voltage Circuit Low
- P05F0Reductant Pump Supply Voltage Circuit High
- P05F2Reductant Pump Supply Voltage Circuit Stuck Off
- P05F3Exhaust Aftertreatment Power Relay Control Circuit Open
- P05F4Exhaust Aftertreatment Power Relay Control Circuit Low
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.