Powertrain, generic · Hybrid propulsion

P0B3A Motor Electronics Coolant Pump B Control Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P0B3A sets when the control signal of motor electronics coolant pump B stays higher than expected, typically a short to battery voltage on the command line or, with some driver designs, an open pump input that floats high. The module then cannot switch the pump as requested. No manufacturer documents P0B3A publicly. As reference points, FCA has a pump B on its 4xe models with the performance code P0C74, and Ford lists the pump A high code P0A07 among PCM codes fixed by a battery controller update on the 2020 Explorer and Aviator hybrids. CARB requires inverter thermal management outputs to be monitored. Open and low faults are P0B38 and P0B39. Overheating protection may reduce power.

Likely causes

Control wire shorted to battery voltage
Pump control input open so the line floats high
Controller software misjudging the circuit, fixed by update
Driver stage in the controlling module faulty

Symptoms

  • MIL and hybrid or coolant warning
  • Pump cannot be switched off or on as commanded
  • Reduced electric power when the inverter heats up

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–600
Time0.5–3 h

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

Parts involved

motor electronics coolant pump bwiring harnesshybrid control module

Related codes

P0B38P0B39P0C74P0A07P2D05

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