Powertrain, generic · Hybrid propulsion

P0C3B DC/DC Converter Temperature Sensor A High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P0C3B reports a signal from DC/DC converter temperature sensor A above its valid range, typically a short to positive or an open circuit pulled up by the input. Mercedes-Benz documents it on series 243 (EQB) and 465 (G-Class, including the electric G 580): information LI54.10-P-079533 describes P0C3B00 as a short circuit to positive of temperature sensor A, stored together with P0E9700, P0E5400 and P0C4000 after faulty wake-up behaviour of the converter. Drivers see a red 12 V battery message and white or yellow HV warnings. The remedy is a converter check in XENTRY, clearing the fault memory and a converter reset; parts are not replaced first. The low-signal sibling is P0C3A, sensor B's high code is P0C40.

Likely causes

Faulty wake-up behaviour of the converter putting it into an error state (Mercedes 243/465)
Open circuit or short to positive in the sensor A circuit
Internal defect of the DC/DC converter

Symptoms

  • Red 12 V battery warning in the cluster
  • White or yellow high-voltage system warning
  • 12 V battery no longer charged while driving

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€80–2,500
Time0.5–4 h

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

Parts involved

dcdc converter temp sensor awiring harnessdcdc converter

Related codes

P0C3AP0C38P0C39P0C3CP0C40P0E54

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