Engine Coolant Temperature Sensor Circuit Low
Coolant temperature sensor signal is too low for normal operation.
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What it means (plain English)
The engine coolant temperature sensor measures how hot the engine coolant is. When it reports a value that's too low, it can make the engine run poorly or cause it to not start because the computer thinks the engine is cold.
What the computer is actually seeing
The engine control module (ECM) looks for a voltage signal from the coolant temperature sensor, in the range of 0.5V to 4.5V. A reading below 0.5V indicates a problem, signaling that the coolant is too cold, potentially disrupting fuel injection and ignition timing.
What a healthy reading looks like
Coolant temperature sensor should show between 190-220°F (88-104°C) when the engine is warm and running.
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 coolant level to ensure it's adequate. Low coolant can affect readings.
- 22. Inspect the wiring and connectors of the coolant temperature sensor for damage or corrosion. Repair any issues found.
- 33. Use a scan tool to read the value of the coolant temperature sensor. It should read between 190-220°F (88-104°C) when the engine is warm. If it reads below 0.5V, there's an issue.
- 44. If the sensor reading is still low, disconnect the sensor and measure the voltage directly at the connector with the ignition on (engine off). It should be close to 5V. If it’s low, check ECM power and ground.
- 55. If the voltage is good but the sensor still reads low when connected, replace the coolant temperature sensor.
Common causes
- Faulty engine coolant temperature sensor
- Wiring issues or connector problems
- Short to ground in the sensor circuit
- ECM software issue
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Moderate severity means you should fix it soon. It can affect engine performance and emissions.
Will this problem come back after repair?
If properly diagnosed and fixed, it should not return unless there's an underlying issue with the wiring or ECM.
Why does this code sometimes come with SPN 110?
SPN 110 is typically related to the coolant temp sensor performance, and both codes can trigger if there’s a sensor issue or a wiring problem.
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