P0C3A: DC/DC Converter Temperature Sensor A Low

P0C3A means the signal of DC/DC converter temperature sensor A is below its valid range. Low refers to the signal voltage: with an NTC thermistor and pull-up, as GM uses for its hybrid temperature sensors, a short to ground or a failed element reads as extreme heat. No manufacturer documents P0C3A publicly. Mercedes-Benz shows the opposite case for the same sensor, P0C3B as a short to positive, on the EQB and the G-Class, and Ram the plausibility code P0C39. CARB requires the converter's inputs to be checked for out-of-range values. Because the controller must assume an overheated power stage, it limits or stops the converter output; the 12 V battery then supplies the car alone and a low-voltage warning may follow. The sensor is usually built into the converter.

Symptoms

• Hybrid or EV system warning
• 12 V battery warning, system voltage dropping
• Reduced power or restricted functions

Most likely causes

• Sensor A signal shorted to ground inside the converter or its harness
• Shorted temperature element A, usually requiring converter replacement
• Converter really overheated due to a cooling fault

What to check, in order

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

1. Read the codes with a hybrid-compatible scanner and write down the freeze frame data
2. With the connector unplugged, check whether the signal wire is making contact with ground.
3. Make sure the battery cooling air intake is clean
4. Check the 12 V auxiliary battery, which can also trigger warnings
5. 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 P0C3A means

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

Frequently asked questions

Can I keep driving with code P0C3A?

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 P0C3A?

The most common causes are: sensor A signal shorted to ground inside the converter or its harness; shorted temperature element A, usually requiring converter replacement; converter really overheated due to a cooling fault.

Related codes

• P0C3BDC/DC Converter Temperature Sensor A High
• P0C38DC/DC Converter Temperature Sensor A Circuit
• P0C39DC/DC Converter Temperature Sensor A Range/Performance
• P0C3CDC/DC Converter Temperature Sensor A Intermittent/Erratic
• P0C3FDC/DC Converter Temperature Sensor B Low
• P0D32DC/DC Converter A Over Temperature

Sources

• law.cornell.edu: 13 CCR 1968.2
• static.nhtsa.gov: MC 11021800 0001
• gsi.ext.gm.com: 16OBDG02 Hybrid Diagnostics

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.