Cooling System Temperature Sensor A

The sensor that monitors engine coolant temperature is reporting a problem, which might mean the engine is overheating or the sensor itself is faulty.

The engine control unit (ECU) receives a voltage signal from the cooling temperature sensor that usually fluctuates between 0.5 volts (cold) to 4.5 volts (hot). If this signal is outside of the expected range, it triggers the code.

Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.

1. 11. Check the engine coolant level. It should be between the low and high marks. If low, top off and check for leaks.
2. 22. Inspect the wiring and connectors of the coolant temperature sensor for damage or corrosion. Repair as needed.
3. 33. Use a scan tool to check the actual temperature reading from the cooling system. It should match the coolant temperature based on your mechanical gauge or infrared thermometer.
4. 44. If the reading from the sensor is not within 90°C to 110°C while the engine is running hot, replace the cooling temperature sensor and retest.
5. 55. If the sensor checks out, verify the operation of the thermostat by checking temperature differences between inlet and outlet hoses. If the inlet stays cold, replace the thermostat.

• Faulty cooling temperature sensor
• Wiring or connector damage
• Low coolant level or leaks
• Thermostat stuck closed
• ECU failure

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