Powertrain, generic · Hybrid propulsion

P0C31 Inverter B Cooling System Performance

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P0C31 reports that the cooling circuit of a second power inverter does not remove heat as expected; inverter A has its own code, P0A93. Vehicles with two separately cooled power electronics units, for example a front and a rear drive unit, need this second code. CARB requires hybrid OBD to monitor the parts used for inverter thermal management and, where feasible, to check the cooling performance itself. No manufacturer documents P0C31 publicly. For the analogous P0A93, Hyundai's 2011 Sonata Hybrid bulletin 14-HC-001 points to the electric water pump, and coolant pump faults of the B circuit are reported as P0B38 or P0C74. To protect the semiconductors the controller limits motor power. A low coolant level or trapped air is worth checking first.

Likely causes

Low coolant level or air trapped in the inverter B circuit
Weak or failed electric coolant pump of the circuit
Clogged radiator or inoperative cooling fan

Symptoms

  • Hybrid or EV system warning and MIL
  • Reduced drive power, especially under load or in heat
  • Coolant level low in the electronics reservoir

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–1,500
Time0.5–4 h

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

Parts involved

inverter binverter b cooling

Related codes

P0A93P0B38P0C74P0C73P2C72

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