Powertrain, generic (extended)

P26B0 Engine Coolant Bypass Valve B Range/Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P26B0 covers a valve B that is electrically sound but does not perform: it moves too slowly, stops short of its target or reports a position that does not match the command. No manufacturer publishes criteria for P26B0. The closest public example is GM's logic for the valve A counterpart P26A3 on the 2011 Volt, Type B, which fails the valve when an end-position learn above 50 °C coolant fails or the commanded position is not reached within 15 s. Ford, which defines valve B as its transmission cooling valve, lists only circuit codes for it. Under CARB, an output that can affect emissions needs a functional check where feasible. Sluggish valves from contaminated coolant, worn gears or a weak motor are the expected causes.

Likely causes

Valve moving slowly due to contaminated or wrong coolant
Worn gear train or weak valve motor
Low supply voltage or high resistance in the drive circuit

Symptoms

  • Check engine light
  • Engine or transmission temperature outside its normal band

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€0–800
Time0.3–3 h

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

Parts involved

coolant bypass valve bthermostat housing

Related codes

P26A3P26AFP26B2P26AC

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