P0C3B: DC/DC Converter Temperature Sensor A High

What it means

The DC/DC converter temperature sensor A circuit signal is higher than expected.

At a glance

• Usually lights the check-engine light
• The engine or gearbox may go into limp mode

How it works

DC/DC converter temperature sensor A sends a temperature signal to the hybrid control system. The module monitors its electrical level, and P0C3B sets when the signal is higher than the expected range. An open circuit or short to voltage can cause this high reading even if the converter is not actually overheated.

Common causes

Most likely first.

1. Open circuit in the sensor wiring
2. Short to voltage in the sensor circuit
3. Faulty temperature sensor

Symptoms

• Hybrid-system warning light may illuminate
• Reduced power or limited hybrid operation
• DC/DC converter may limit output to protect itself

How to diagnose it

1. Check freeze-frame and live data to see whether sensor A is stuck high or changes with converter operation.
2. Inspect the sensor A connector and wiring for a loose connection, broken conductor, corrosion, or heat damage.
3. Check sensor A's circuit for an open or short to voltage using the wiring diagram and manufacturer's procedure.
4. Test sensor A and the circuit at the connector against the manufacturer's specifications.
5. Repair the open, short, or connection fault, or replace sensor A if it fails testing, then confirm the temperature reading is credible.

Common fixes

• Secure the connector and repair damaged sensor A terminals.
• Repair an open or short-to-voltage condition in sensor A wiring.
• Replace sensor A if it fails the specified test.

Can I keep driving?

Avoid sustained high electrical loads while sensor A's high signal is unresolved, since the converter may limit output or its temperature protection may not work reliably. Stop safely if electrical functions or vehicle power deteriorate.