Powertrain, generic · Hybrid propulsion

P0C3F DC/DC Converter Temperature Sensor B Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P0C3F is stored when the voltage from the second temperature sensor of the DC/DC converter falls below the lowest plausible value. These sensors are normally NTC thermistors fed through a pull-up resistor, so a low voltage corresponds to an extremely hot reading; a short to ground or a shorted element produces exactly that. No manufacturer documents P0C3F publicly. GM uses the same logic for comparable hybrid thermistors, flagging a low circuit once the computed temperature reaches about 88 °C. Mercedes-Benz lists the opposite fault of the same sensor, P0C40, on the EQB and G-Class. CARB requires hybrid component inputs to be checked for out-of-range signals. The converter usually derates to protect itself, so 12 V charging suffers. Sensor A's low code is P0C3A.

Likely causes

Sensor B signal line shorted to ground in the converter or harness
Shorted thermistor B, usually only fixable by replacing the converter
Converter actually overheating because its cooling fails

Symptoms

  • Hybrid or EV system warning in the cluster
  • 12 V battery warning or falling on-board voltage
  • Reduced power or switched-off comfort consumers

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€150–2,500
Time1–4 h

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

Parts involved

dcdc converter temp sensor bwiring harnessdcdc converter

Related codes

P0C3DP0C3EP0C40P0C41P0C3AP0D32

References: law.cornell.edu, gsi.ext.gm.com, static.nhtsa.gov.