Engine Cooling System Temperature Sensor Fault
Indicates a problem with the engine cooling temperature sensor.
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What it means (plain English)
The engine's computer is getting a reading from the cooling system temperature sensor that doesn't match what it expects, which could indicate the sensor is faulty or there's an issue with the wiring.
What the computer is actually seeing
The engine control module (ECM) expects the cooling temperature to be between 180°F to 220°F while running but it's getting a signal that's too high or too low, typically below 32°F or above 250°F.
What a healthy reading looks like
Normal sensor output should be between 0.5V to 4.5V, corresponding to temperatures from -40°F to +248°F.
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 in the reservoir—must be at recommended level. If low, top it up and recheck for codes.
- 2Inspect wiring and connectors at the temperature sensor for damage or corrosion. Repair any issues found before moving on.
- 3Using a multimeter, check the voltage output of the cooling temperature sensor. A sensor output should generally be between 0.5V to 4.5V; if it's outside this range, replace the sensor.
- 4Clear the fault codes and run the engine to see if the code reappears. If it does, replace the cooling temperature sensor.
Common causes
- Faulty cooling temperature sensor
- Wiring issues or broken connectors
- Coolant level too low
- Thermostat malfunction
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 without addressing the issue; it can lead to overheating or poor engine performance.
Will this code come back after resetting?
Yes, if the underlying issue isn't resolved, the code will reappear.
Why does this code often pair with SPN 1102?
SPN 1102 often indicates a fault with the secondary temperature sensor, which works alongside SPN 1191; both deal with temperature readings affecting engine performance.
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