Engine Coolant Temperature Sensor Voltage Out of Range

The computer is getting a reading from the coolant temperature sensor that is outside of its normal range, which means it's either way too high or too low compared to what it expects.

The ECU is monitoring the coolant temperature sensor voltage, which should typically range from 0.5V (cold) to 4.5V (hot). If the voltage is below 0.2V or above 4.8V, a fault is triggered.

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. 1Check the coolant level in the reservoir and ensure it's at the correct level. No further testing if it's low.
2. 2Inspect the wiring and connectors of the coolant temperature sensor. Look for frayed wires or poor connections.
3. 3Measure the voltage at the coolant temperature sensor. Expect between 0.5V-4.5V with the engine at normal operating temperature.
4. 4If voltage readings are out of range, replace the coolant temperature sensor and retest.
5. 5If voltage is in range but the code persists, check the ECU for faulty or outdated software.

• Open circuit in sensor wiring
• Shorted sensor or wiring
• Failed coolant temperature sensor
• Poor connection at the sensor
• Corroded terminals or connectors

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