P26F4 Coolant Pump C Control Circuit/Open

Coolant pump C is a third electric pump next to pumps A and B; which circuit it serves is defined by each manufacturer. In Bentley's V8 models from the Volkswagen group it is the auxiliary pump for the heater circuit, while GM's diesel tables use the C codes for the pump of the low-temperature loop. P26F4 means the control line to this pump is open, so the module cannot command it or receives no feedback. No manufacturer documents P26F4 itself in public; the closest case is Bentley's bulletin 2058340/1 on the low-side code P26F5, where an internally corroded pump led to a lit MIL. CARB requires circuit checks on electric components that affect emissions or other monitors. Depending on the loop, heater output drops or charge air and electronics are cooled less.

Likely causes

Symptoms

• Check engine light on
• Weak cabin heating at idle or with the engine stopped
• Higher charge air or component temperatures, depending on the loop

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, gsi.ext.gm.com.