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

P05ED Reductant Heater Control Module Supply Voltage

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

Some diesels use a separate control module or power stage for the DEF heaters in tank, pump and lines; without heating, frozen fluid cannot thaw in winter and dosing stays blocked. P05ED reports that this module's supply voltage is outside its allowed window – a blown main fuse, an open feed or ground, or system voltage too low or too high. 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). Thresholds are not published; GM's L5P monitors the comparable heater supply under its own codes and flags a drop of more than 3 V below battery voltage while heating is requested. Start with fuse, feed, ground and battery or charging system.

Likely causes

Main fuse or feed wire to the heater module faulty, connector corroded (splash zone)
Poor module ground
Weak battery or charging fault (system voltage too low or too high)
Heater control module faulty internally

Symptoms

  • Check engine light on
  • DEF/AdBlue warning, possibly countdown to no-restart
  • In cold weather: DEF frozen, dosing blocked, further heater codes

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–700
Time0.5–3 h

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

Parts involved

reductant heater control modulemodule power supplybattery

Related codes

P05F8P20B9P21C2P21CBP0562P0563

References: law.cornell.edu, static.nhtsa.gov, gsi.ext.gm.com, data.epo.org.