Powertrain, generic (extended)

P26BE Engine Coolant Bypass Valve D Control Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P26BE flags a drive circuit of valve D that reads too low, normally because the wiring or the valve itself is grounded. No manufacturer documents P26BE publicly. Ford, whose valve D is the cabin heating valve, reports only the general circuit code P26BD and, from 2024, the short-to-battery code P26BF. The closest documented logic belongs to valve C: GM's 2025 diesel table looks for grounded lines on that valve's H-bridge in each motor direction and grades it Type B. CARB requires output circuits to be monitored for circuit faults. A grounded line may keep a low-side driven valve energised or make the driver cut out. On a heater valve the result is mostly wrong cabin temperature, though a valve in the engine loop can also upset warm-up.

Likely causes

Drive wire shorted to ground
Internal short in valve D
Moisture or corrosion in the connector

Symptoms

  • Check engine light
  • Cabin heat stuck at full or at minimum
  • Valve D does not react to commands

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–500
Time0.5–2.5 h

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

Parts involved

coolant bypass valve dsolenoidwiring harness

Related codes

P26BDP26BFP26B8

References: law.cornell.edu, fordservicecontent.com, gsi.ext.gm.com.