P0A00: Motor Electronics Coolant Temperature Sensor A Circuit

General circuit fault on temperature sensor A in the separate coolant loop that cools the inverter and other drive electronics of a hybrid or electric vehicle. The module flags it when the sensor signal cannot be used at all, without a more specific low, high or plausibility verdict; those cases have their own codes P0A01 to P0A04. No manufacturer documents P0A00 publicly. GM's Two-Mode hybrid trucks monitor the same sensor only through P0A01 to P0A03, and CARB requires every input of the inverter thermal management to be checked for circuit faults. Without a valid reading the control unit usually limits electric drive power to protect the electronics.

Medium severity. Can I keep driving?Watch the temperature gauge. If it climbs or a warning appears, stop the car in a safe place and turn off the engine: overheating can cause serious damage.

Symptoms

Hybrid system or check engine warning light
Reduced electric drive power
Inverter coolant pump or radiator fan running constantly as a precaution

Most likely causes

Corroded or loose connector at the sensor in the inverter coolant loop
Temperature sensor element failed
Damaged signal or reference wire between sensor and hybrid control module
Fault in the input stage of the hybrid or inverter control module

What to check, in order

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

With the engine cold, check the coolant level; never do this when the system is hot
Check the actual temperature in live data
Make sure the fan comes on when it should
Check the thermostat and connector
Measure the sensor and replace it if its readings do not make sense

Good to know

Repair difficulty: medium
It can trigger limp mode.
It affects emissions.

What each character of P0A00 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
A: Hybrid or air and fuel
00: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0A00?

Watch the temperature gauge. If it climbs or a warning appears, stop the car in a safe place and turn off the engine: overheating can cause serious damage.

What causes code P0A00?

The most common causes are: corroded or loose connector at the sensor in the inverter coolant loop; temperature sensor element failed; damaged signal or reference wire between sensor and hybrid control module.

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.