Engine Coolant Temperature Sensor 1 Voltage Low
Engine coolant temperature sensor input is low.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The computer expects a voltage signal from the coolant temperature sensor, but it's getting less than 0.15 volts, which indicates a problem with the sensor or wiring.
What the computer is actually seeing
The Engine Control Unit (ECU) reads a voltage from the coolant temperature sensor, typically between 0.5 and 4.5 volts. A reading under 0.15 volts triggers this fault code.
What a healthy reading looks like
Expected voltage from the coolant temperature sensor should be between 0.5 - 4.5 volts at operating temperature.
Guided diagnostic — the DiagCoach way
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.
- 11. Check coolant level. Ensure it’s at the proper level; fill if necessary. Go to step 2.
- 22. Inspect the wiring and connectors between the sensor and the ECU. Look for signs of damage or corrosion. Repair as needed. Go to step 3.
- 33. Using a multimeter, test the voltage at the coolant temperature sensor plug with the engine running. You should see between 0.5 and 4.5 volts. If less than 0.15 volts, go to step 4. If you have proper voltage, replace the sensor.
- 44. Disconnect the sensor and measure its resistance with the engine cold and then hot. You should see changes in resistance values as temperature changes (approximately 2000 ohms at 32°F to about 235 ohms at 195°F). If not, replace the sensor.
Common causes
- Faulty coolant temperature sensor
- Open or shorted wiring in the sensor circuit
- Corroded or loose connector at the sensor or ECU
- Low coolant level affecting sensor readings
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Yes, but monitor for overheating and fix as soon as possible to avoid engine damage.
Will this code clear itself?
It may clear if the underlying issue is fixed and the ECU does not detect the fault after several start cycles.
Why does this code sometimes pair with SPN 190?
SPN 190 is related to a general coolant temperature issue; both codes indicate there’s a problem with the coolant temperature readings.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
Start guided diagnostic →