Powertrain, generic · Hybrid propulsion

P0B39 Motor Electronics Coolant Pump B Control Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P0B39 sets when the control signal of motor electronics coolant pump B is lower than the controller expects, usually a short to ground on the command line or a pump input that pulls the line down. On a low-side switched or PWM line the module sees the voltage stuck low while it commands the pump off. No manufacturer documents P0B39 publicly. Pump B is in service at FCA (Compass and Renegade 4xe, performance code P0C74), and Ford stores the pump A codes P0A06 and P0A07 in the PCM of the 2020 Explorer and Aviator hybrids. CARB requires these inverter cooling outputs to be checked for circuit faults. Open and high faults are P0B38 and P0B3A; running faults use P0C74 and P2D05 ff.

Likely causes

Control wire shorted to ground, often chafed at brackets
Pump electronics pulling the control input low
Coolant or water in the pump connector
Driver stage in the controlling module faulty

Symptoms

  • MIL and hybrid or coolant warning
  • Pump runs permanently or not at all, depending on circuit design
  • Power limitation at high load or heat

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

P0B38P0B3AP0C74P0A06P2D08

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