Engine Coolant Temperature Sensor 1
Indicates a fault with the engine 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 engine coolant temperature sensor tells the computer how hot the coolant is, which affects fuel injection and exhaust treatment. If it fails, the computer can't properly adjust these parameters, causing poor performance or emissions.
What the computer is actually seeing
The engine control module (ECM) expects a voltage between 0.5V (cold) and 4.5V (hot). If the reading falls outside this range, it triggers the fault code.
What a healthy reading looks like
Coolant temperature should read approximately 195°F (90°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.
- 11. Check the coolant level; ensure it's at the proper level to avoid false readings.
- 22. Inspect the wiring and connector for damage or corrosion.
- 33. Using a multimeter, check the resistance of the coolant temperature sensor at various temperatures (should be around 2000-3000 ohms at 68°F/20°C).
- 44. Compare the resistance readings with the manufacturer's specifications.
- 55. If readings are out of spec, replace the coolant temperature sensor.
- 66. Clear the fault code and monitor for reoccurrence.
Common causes
- Failed coolant temperature sensor
- Wiring issues (frayed or damaged wires)
- Corroded or poor connections
- Coolant leaks affecting sensor readings
Typical repair cost
$$ - $$$
Related codes
Frequently asked questions
Is it safe to drive with this code present?
It's moderately safe, but expect poor performance and potential emissions issues. Fix soon.
Will this code come back after clearing?
If the underlying issue isn't resolved, it will likely return.
Why does it pair with other codes?
It often indicates related issues with temperature or engine management components.
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