Engine Cooling System Temperature Sensor 1 High
Indicates that the engine cooling temperature sensor 1 is reading higher than expected.
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What it means (plain English)
The engine's computer thinks the coolant is hotter than it should be based on the temperature sensor.
What the computer is actually seeing
The engine control module (ECM) interprets inputs from the coolant temperature sensor, expecting a range typically between 180°F to 220°F. If the reading goes above 240°F, a fault is triggered.
What a healthy reading looks like
Coolant temperature readings for normal operation should be between 180°F to 220°F. A reading above 240°F is considered erratic.
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 first. Low coolant can affect readings. If low, top it off and see if the code comes back.
- 2Inspect the wiring and connector to the coolant temperature sensor for damage, corrosion, or loose connections.
- 3Measure the coolant temperature sensor resistance with a multimeter; expect about 0.5kΩ at 180°F. Replace if out of range.
- 4Start the engine and monitor the coolant temperature with a scan tool. Ensure it matches the gauge reading on the dash. If not, replace the sensor.
Common causes
- Faulty coolant temperature sensor
- Wiring issues or bad connection to the sensor
- Coolant leaks or low coolant level
- Thermostat stuck closed or malfunctioning
- ECM software issues
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Moderate severity means it’s best to fix soon; overheating can lead to severe engine damage.
Will this code come back after I reset it?
Yes, if the underlying problem isn't fixed, the code will likely return.
Why do I see this code along with SPN 110?
SPN 110 generally indicates a low temperature reading, so the two codes can appear together when the sensor is malfunctioning.
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