P2B6C Coolant Pump D Overspeed/Air in System

P2B6C means coolant pump D is spinning faster than its command would explain, the signature of an impeller moving air instead of liquid. No manufacturer documents this exact code publicly. For pump B, Bentley stores the counterpart P2B6500 on W12 models and traces it to a restricting vent hose, and Ford lists P2B65 as failure type B1 (overspeed/dry run). Patent EP2743509A1 describes how dry running and air bubbles in an electric coolant pump can be recognised from the way its speed rises and decays after a defined energy input. Typical causes are a low level after a leak, incomplete bleeding after service and air pockets that gather at high points of the loop. Bleed the circuit with the manufacturer's routine and look for leaks. A stalled pump D is P2B6A.

Likely causes

Symptoms

• Coolant warning or rising temperature display
• Gurgling from the cooling circuit
• Coolant level drops in the expansion tank

Repair estimate

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

Parts involved

Related codes

References: law.cornell.edu, fordservicecontent.com, static.nhtsa.gov, patents.google.com.