P26F6 Coolant Pump C Control Circuit High

P26F6 is stored when the control line of coolant pump C carries a higher voltage than the commanded state allows. In practice that means the wire touches a live circuit, the pump has lost its ground so the line floats up, or the line is open between driver and pump in a way the output stage reads as high. No public service document covers P26F6 itself. The low-side sister P26F5 is documented by Bentley for the auxiliary heater pump of its VW-group V8 models, where internal corrosion and pump self-diagnosis were the causes; CARB requires electric parts serving emission control or other monitors to be checked for such circuit faults. A pump held permanently on may keep running after the engine is switched off and drain the battery; one that cannot start leaves its loop without flow.

Likely causes

Symptoms

• Check engine light on
• Pump runs on after switch-off or does not run at all
• Weak heater output with the engine idling

Repair estimate

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

Parts involved

Related codes

References: law.cornell.edu, static.nhtsa.gov.