Coolant Temperature Sensor Range/Performance Problem
The engine control module detects an issue with the coolant temperature sensor.
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 coolant temperature sensor measures how hot the engine coolant is. If it's reading out of range—like way too high or too low—the computer doesn't know if the engine is running hot or cold, which can lead to bad performance or damage.
What the computer is actually seeing
The engine control module expects coolant temperature readings typically between 180°F and 220°F (82°C to 104°C). If it sees a value outside this range, it will trigger the fault code.
What a healthy reading looks like
Coolant temperature readings should be between 180°F and 220°F (82°C to 104°C) during normal operation.
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.
- 1Check the coolant level—ensure it's at the proper level and not low.
- 2Inspect the connector and wiring to the coolant temperature sensor for damage or corrosion.
- 3Using a multimeter, measure the voltage at the coolant temperature sensor. At operating temperature, expect around 0.5V to 4.5V depending on the engine temperature. If out of this range, proceed to the next step.
- 4Test the coolant temperature sensor by removing it and placing it in a pot of water. Heat the water and measure the resistance. At 200°F (93°C), it should show specific resistance values (check OEM specs). If it’s off, replace the sensor.
- 5If the sensor checks out, check for faults in the ECM. Use a professional scan tool to see if other related DTCs are present.
Common causes
- Faulty coolant temperature sensor
- Wiring issues (shorts or opens)
- Faulty engine control module (ECM)
- Corrosion or poor connection at the sensor or wiring harness
Typical repair cost
$$ - $$$ (sensor: $50-$150; labor: $100-$200)
Related codes
Frequently asked questions
Can I still drive the vehicle?
It's better to fix it soon, as poor readings can affect engine performance and emissions.
Will this code come back after I clear it?
It could return if the underlying issue isn't addressed, like a bad sensor or wiring issue.
Why did this code pair with SPN 3900?
Both relate to temperature sensing issues, indicating possible sensor or signal problems.
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