Powertrain, generic (extended)

P2B6D Engine Coolant Flow Control Valve Position Sensor Circuit Intermittent/Erratic

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2B6D covers a position signal from the engine coolant flow control valve that drops out or jumps for short moments, even though single readings may still lie inside the valid window. This exact code appears in no public manufacturer document. In GM's 3.0 L Duramax diesel the valve sends its angle digitally via SENT; the engine computer tests that sensor for a low reading (P2B5E, under 2 %), a high reading (P2B5F, over 98 %) and plausibility (P2B60, more than 12 % deviation) and treats lost SENT communication as a separate fault, but names no intermittent code. A system using P2B6D would count unstable readings, for instance from a loose terminal, fretting corrosion or a harness that moves with the engine. Input faults of this kind must be caught according to CARB 13 CCR 1968.2 (e)(15). Coolant flow control becomes unreliable.

Likely causes

Loose or widened terminal in the valve connector
Fretting corrosion on the signal or reference pins
Harness rubbing or flexing with engine movement
Position sensor inside the valve unstable

Symptoms

  • Warning lamp, code often stored as intermittent
  • Temperature display or warm-up behaviour fluctuates

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–1,200
Time0.5–4 h

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

Parts involved

engine coolant flow control valvewiring harnessecm

Related codes

P2B5DP2B5EP2B5FP2B60P2B61

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