P0C3C: DC/DC Converter Temperature Sensor A Intermittent/Erratic

P0C3C covers a signal from DC/DC converter temperature sensor A that drops out or jumps for short moments while staying mostly within range. The heat sink of a converter warms and cools slowly, so fast jumps point to the signal path rather than to real temperature changes. No manufacturer documents P0C3C publicly. The method is known from GM's hybrid tables for comparable thermistors, such as P0C37 for battery sensor F: the controller adds up signal changes in short windows and fails the test when several windows exceed a limit. CARB requires such inputs to be monitored for faults. Typical causes are a loose terminal, vibration damage or moisture at the converter connector. Unlike P0C3A and P0C3B, the fault may vanish between tests, so a wiggle test helps.

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

Intermittent hybrid or EV warning
Occasional 12 V charging interruptions

Most likely causes

Loose terminal or moisture at the converter connector
Harness damaged by vibration with intermittent contact
Intermittent fault inside the converter

What to check, in order

Start with the simplest. You can tick off each step.

Read the codes with a hybrid-compatible scanner and write down the freeze frame data
Gently move the wiring with the engine running and watch whether the reading changes.
Make sure the battery cooling air intake is clean
Check the 12 V auxiliary battery, which can also trigger warnings
Leave any high-voltage measurements to a specialized repair shop

Good to know

It can trigger limp mode.
It affects emissions.

What each character of P0C3C means

P: Powertrain: engine and transmission
0: Generic code: same on every make
C: Subsystem depends on the code range
3C: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0C3C?

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 P0C3C?

The most common causes are: loose terminal or moisture at the converter connector; harness damaged by vibration with intermittent contact; intermittent fault inside the converter.

Related codes

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.