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

P05EF Reductant Pump Supply Voltage Circuit Low

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. P05EF means the supply voltage is too low or the supply line is shorted to ground. GM's 6.6 L diesel monitors the same high-side driver under P1043 (short to ground with driver on, about 0.5 Ω, 3 s, first trip); Ford flags its pump controller voltage below 8.5 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

Supply line shorted to ground (chafed against the frame)
High contact resistance or corrosion in the connector
Pump shorted internally or stiff (high current)
Weak battery or charging system

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.