Engine Coolant Temperature Sensor Circuit Low
The engine coolant temperature sensor is reading a voltage that is too low, indicating a potential fault in the circuit.
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What it means (plain English)
The computer expects the engine coolant temperature to be between 180°F and 220°F, but it's getting a reading close to 0 volts, which suggests a fault in the electrical circuit or the sensor itself.
What the computer is actually seeing
The computer is tracking the voltage from the coolant temperature sensor. If this voltage drops below 0.2 volts or hangs around that level when the engine is running, it triggers this code.
What a healthy reading looks like
Coolant temperature readings should generally be between 180°F (82°C) and 220°F (104°C). The voltage signal from the sensor should be between 0.5 volts to 4.5 volts depending on 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 the engine coolant level. If low, top off and see if the code returns after a drive cycle.
- 22. Inspect the wiring and connector to the coolant temperature sensor for damage or corrosion.
- 33. With the engine running, backprobe the coolant temperature sensor connector. You should see a voltage between 0.5V and 4.5V. If not, replace the sensor.
- 44. If voltage is within range, test continuity from the sensor connector to the ECM (Engine Control Module). If there's no continuity, repair the wiring; if all checks out, consider a faulty ECM.
Common causes
- Faulty coolant temperature sensor
- Wiring issues (damaged or corroded wires)
- Poor connection at the sensor or connector
- Engine coolant leak affecting sensor operation
- Fault in the ECU (rare)
Typical repair cost
$$
Related codes
Frequently asked questions
Can I drive with this code stored?
It's drivable, but the engine might overheat or run poorly due to inaccurate temperature readings. Fix it soon.
Will this code come back after clearing it?
If the underlying issue isn't resolved, yes, the code will likely return after some running conditions.
Why does this code sometimes appear with SPN 4223?
SPN 4223 relates to high voltage. If there's a fault in the circuit, both a low and high voltage code can trigger.
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