Powertrain, generic (extended)

P261E Coolant Pump B Control Circuit Stuck On

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P261E covers the case where coolant pump B keeps working although the module has commanded it off. That can be an output that stays energised, a relay with welded contacts, or, on switchable mechanical pumps, a shroud or valve that no longer closes, so coolant circulates during warm-up. GM's 2014-2018 hybrid tables name P261E only in the flow-stuck-on fault bundle of the switchable water pump, which also blocks the thermostat check P0128; GM does not publish its threshold there. No other manufacturer documents P261E publicly. Its counterpart for pump A, P261F, is set by GM when the feedback speed stays high while the pump is off. A stuck-on pump slows warm-up, raises fuel use and can drain the battery after shutdown.

Likely causes

Pump relay with welded contacts or output stage stuck on
Switchable pump shroud or vacuum/solenoid valve not closing
Control line shorted to battery voltage

Symptoms

  • Engine warms up slowly, heater stays cool longer
  • Pump audible after the engine is switched off
  • Warning lamp and possibly a thermostat code

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–900
Time0.5–3 h

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

Parts involved

coolant pump bcontrol modulewiring harness

Related codes

P261FP261AP261DP261BP0128

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