Powertrain, generic (extended)

P26CD Engine Coolant Pump Control Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P26CD is set when the control circuit of the engine coolant pump shows a higher voltage than the commanded state allows, for example while the driver is switched off. No manufacturer documents this code in public. CARB's OBD rule asks for output components to be monitored for circuit faults, and the same pump circuit is known from its low-side partner P26CC, which Honda documents on its hybrids in bulletin 25-020. Typical high faults are a control wire touching battery voltage, a relay whose contacts weld shut so the pump keeps running, or an open ground on the pump side. Depending on design the pump then runs permanently or cannot be regulated; the engine module usually stores the code at once and lights the MIL, while warm-up may take longer.

Likely causes

Pump control wire shorted to battery voltage
Pump relay contacts stuck closed
Open ground at the pump pulling the circuit high

Symptoms

  • Check engine lamp on
  • Pump running after the engine is switched off
  • Longer warm-up phase

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

engine coolant pumpwiring harness

Related codes

P26CAP26CCP2603P26D5

References: law.cornell.edu, static.nhtsa.gov.