Cooling System Temperature Sensor 1 - Voltage Out of Range

The cooling system temperature sensor is sending a voltage signal that’s either too high or too low. This sensor helps the computer determine how hot the engine is running by providing a voltage that should correspond with the engine’s temperature.

The ECM expects to see a voltage signal between 0.5V (cold) and 4.5V (hot). If the signal is below 0.5V or above 4.5V, this code will trigger because the expected temperature range is not being reported.

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 wiring and connectors to the cooling system temperature sensor for any visible damage or corrosion. Decision: If damaged, repair or replace wires/connectors; if ok, proceed to next step.
2. 22. Verify the engine coolant level; ensure it is at the proper level. Decision: If coolant is low, top it off and see if the code returns; if ok, proceed to next step.
3. 33. Test the voltage at the cooling temperature sensor connector with the engine running. You should get between 0.5V and 4.5V. Decision: If voltage is outside this range, replace the sensor; if within range, check the ECM for faults.
4. 44. If the sensor was replaced or the issue persists, clear the code and take the vehicle for a test drive to see if the code returns. Decision: If the code comes back, further diagnose the ECM or look for intermittent wiring issues.

• Faulty temperature sensor
• Wiring issues for the sensor (shorts or opens)
• Corroded connectors
• Coolant level low or improper engine coolant

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