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

P05F0 Reductant Pump Supply Voltage Circuit High

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. P05F0 means the supply voltage is too high, or voltage is present although the supply is switched off (short to battery). GM's 6.6 L diesel monitors this as P1044 (two trips); Ford flags pump voltage above 16 V or controller voltage above 19 V. No manufacturer document available to us uses this exact code; GM and Ford monitor the same function under their own codes. Without supply the pump cannot build pressure, dosing stops and NOx rises; pressure or SCR efficiency codes may follow.

Likely causes

Pump supply shorted to battery positive in the harness
Overvoltage from the charging system or a jump start
Moisture or corrosion causing leakage current in the connector
Relay or driver does not switch off

Symptoms

  • Check engine light on
  • DEF/AdBlue warning, possibly countdown to no-restart
  • Follow-up codes for low DEF pressure or SCR efficiency

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, gsi.ext.gm.com, fordservicecontent.com.