P0C3B code meaning
DC/DC Converter Temperature Sensor A High
Powertrain system Generic code P0Cxx codes Check engine light
What P0C3B means
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.
P0C3B at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0C3B
- Red 12 V battery warning in the cluster
- White or yellow high-voltage system warning
- 12 V battery no longer charged while driving
Common causes of P0C3B
- Most likelyFaulty wake-up behaviour of the converter putting it into an error state (Mercedes 243/465)
- PossibleOpen circuit or short to positive in the sensor A circuit
- Less likelyInternal defect of the DC/DC converter
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Dcdc converter temp sensor aWiring harnessDcdc converter
What each part of P0C3B means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| C | Area: hybrid propulsion. |
| 3B | The exact fault in that area. |
What to do next
- Note P0C3B and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0C3B
What does P0C3B mean?
P0C3B means "DC/DC Converter Temperature Sensor A High". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P0C3B?
Drive gently and only to a workshop. With P0C3B the car can go into limp mode (reduced power) to protect itself.
Will P0C3B fail an emissions test?
Yes, it can. P0C3B is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0C3B to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will P0C3B clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.