Powertrain, generic (extended)

P26D4 Engine Coolant Pump Supply Voltage Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P26D4 narrows the supply fault of the engine coolant pump down to too low a voltage on its power feed. There is no public manufacturer documentation for this code. CARB's OBD rule requires circuit monitoring for electrical components, and Ford shows how the supply of a smart pump is judged with the general code P26D3: there the PCM infers a dead feed from lost pump communication plus a rising coolant temperature. A low reading, unlike a complete loss, typically comes from a corroded fuse holder or connector, a partially broken wire, a relay with burnt contacts or a short to ground that pulls the line down. The pump may then still run but slowly or with interruptions, so heating and engine temperature may become unsteady; the related P26D0 compares the pump's internal electronics voltage instead.

Likely causes

Corroded fuse holder or connector in the pump feed
Supply relay with burnt contacts
Partial short to ground on the feed wire

Symptoms

  • Check engine lamp on
  • Fluctuating engine temperature or heater output

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€20–900
Time0.3–2.5 h

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

Parts involved

smart coolant pump modulesupply circuitbattery

Related codes

P26D3P26D5P26D0P26CC

References: law.cornell.edu, fordservicecontent.com.