Incorrect Engine Coolant Temperature Data
The engine control unit detected an abnormal coolant temperature signal.
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 engine's computer is getting a temperature reading from the coolant sensor that doesn't match what it expects, usually too high or too low, which can affect engine performance.
What the computer is actually seeing
The ECU is reading coolant temperature sensors that are showing values outside the normal range, typically below 40°F (4°C) or above 240°F (116°C) when the engine should be in operation.
What a healthy reading looks like
Coolant temperature should generally range from 175°F (79°C) to 220°F (104°C) when the engine is at normal 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.
- 1Check coolant level; top off if low and retest.
- 2Inspect wiring and connectors to the coolant temperature sensor for damage or corrosion.
- 3Measure resistance of the coolant temperature sensor; it should match manufacturer specs at known temperatures.
- 4Use a scan tool to observe live data; compare readings to expected temperatures under various operating conditions.
Common causes
- Faulty coolant temperature sensor
- Wiring damage or poor connections
- Engine coolant leaks or low levels
- Faulty engine control module (ECM)
- Thermostat stuck open or closed
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's not recommended to drive for long periods as it can lead to performance issues or overheating.
Will this code come back after clearing?
If the root cause isn't fixed, the code is likely to return after a short time.
Why does this code sometimes pair with SPN 1803?
Both codes deal with coolant temperature discrepancies; if one sensor fails, the other often does too.
Working a real vehicle right now?
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