Powertrain, generic (extended)

P2B5D Engine Coolant Flow Control Valve Position Sensor Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2B5D is the general circuit code for the position sensor of the coolant flow control valve, the feedback that tells the engine computer how far the rotary valve has turned. No manufacturer documents this exact code publicly. GM's 3.0-litre Duramax, whose valve reports its position digitally over a SENT link, covers the sensor through the low and high codes P2B5E and P2B5F and a separate communication check instead. A system using P2B5D would flag an implausible or missing signal that fits neither low nor high. CARB 13 CCR 1968.2 (e)(15) requires such input circuits to be checked for continuity. With no valid position the engine computer cannot regulate coolant flow and usually parks the valve in a safe position.

Likely causes

Loose or corroded terminals at the valve connector
Signal, reference or ground wire of the sensor interrupted
Position sensor inside the valve faulty

Symptoms

  • Check engine light on
  • Coolant flow control in fallback, warm-up or heating behaviour changed

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–1,500
Time0.5–8 h

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

Parts involved

engine coolant flow control valvewiring harnessecm

Related codes

P2B5EP2B5FP2B60

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