P0C3D is the general circuit code for the second temperature sensor of the DC/DC converter, which turns high-voltage battery power into 12 V supply. Converters with two sensors watch separate parts of the power stage or cross-check one sensor against the other. No manufacturer documents P0C3D publicly. Sensor B itself appears in bulletins: Mercedes-Benz lists P0C4000, a short to positive of sensor B, on the EQB and the G-Class, and Ram the plausibility code P0C3E as temperature sensor 2 on the 2021 1500 eTorque. Sensor A uses P0C38 for the same fault class. CARB requires such converter inputs to be monitored. A circuit fault makes the controller limit or stop the converter, so the 12 V battery may run down and warnings follow.
High severity. Can I keep driving?If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.
Symptoms
- Hybrid or EV system warning
- 12 V battery warning
Most likely causes
- Connector or wiring fault in the sensor B circuit
- Failed temperature element B inside the converter
- Converter or hybrid control software misjudging the sensor
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- It can trigger limp mode.
- It affects emissions.
What each character of P0C3D means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- C: Subsystem depends on the code range
- 3D: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0C3D?
If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.
What causes code P0C3D?
The most common causes are: connector or wiring fault in the sensor B circuit; failed temperature element B inside the converter; converter or hybrid control software misjudging the sensor.
Related codes
- P0C3EDC/DC Converter Temperature Sensor B Range/Performance
- P0C3FDC/DC Converter Temperature Sensor B Low
- P0C40DC/DC Converter Temperature Sensor B High
- P0C41DC/DC Converter Temperature Sensor B Intermittent/Erratic
- P0C38DC/DC Converter Temperature Sensor A Circuit
Sources
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.