Powertrain, generic · Vehicle speed, idle control and auxiliary inputs

P05F1 Reductant Pump Supply Voltage Circuit Stuck On

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

The electric supply pump in the diesel exhaust fluid (DEF, AdBlue) tank module builds the dosing pressure for the SCR catalyst. Its supply voltage is monitored separately from the pump control circuit (P208A ff); CARB requires SCR components and their outputs to be checked for circuit faults and function. P05F1 means the pump supply stays on although the module switches it off – typically detected after the switch-off command, e.g. during after-run, when the feedback still shows voltage. A welded relay or a shorted semiconductor switch is the usual reason. Chrysler (FCA) lists this code among those that trigger the DEF inducement: a 'Service DEF System' warning, a countdown after 50 miles and no restart after 150 miles (P241D). Without supply the pump cannot build pressure, dosing stops and NOx rises; pressure or SCR efficiency codes may follow.

Likely causes

Pump supply relay stuck (welded contacts)
Semiconductor driver shorted
External voltage or short to positive in the harness
Software or calibration fault

Symptoms

  • Check engine light on
  • DEF/AdBlue warning, possibly countdown to no-restart
  • Follow-up codes for low DEF pressure or SCR efficiency
  • Pump keeps running after switch-off, battery drains

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–900
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

reductant pumpreductant pump supply circuitengine control module

Related codes

P208AP208CP208DP20E8P21CBP21CC

References: law.cornell.edu, static.nhtsa.gov, gsi.ext.gm.com, fordservicecontent.com.