Engine Coolant Temperature Sensor 1
Indicates an issue 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)
This code means the engine computer is getting an unexpected signal from the coolant temperature sensor, which could be sending too high or too low of a voltage, affecting engine performance.
What the computer is actually seeing
The engine control module expects the resistance from the coolant temperature sensor to change as temperature changes. Typically, it should read between 0.3 to 3.0 volts at normal operating temperature (around 190°F to 210°F).
What a healthy reading looks like
Normal coolant temperature sensor voltage should range from 0.3V (around 32°F) to 4.5V (around 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 the coolant level and ensure it’s within the manufacturer’s specified range. If low, top it off and reset the code.
- 2Inspect the wiring and connectors to the coolant temperature sensor for damage, corrosion, or loose connections. Repair as necessary.
- 3Using a multimeter, measure the voltage at the coolant temperature sensor connector with the engine at operating temperature. Is it within expected values?
- 4If voltage is out of range, replace the coolant temperature sensor and clear the codes. If it’s good, check the engine control module for faults.
Common causes
- Faulty coolant temperature sensor
- Wiring harness damage or corrosion
- Short to ground in circuit
- Coolant leaks affecting sensor operation
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Yes, but it may affect fuel efficiency and engine performance. Monitor the temperature gauge closely.
Will this code come back after clearing?
If the sensor is faulty or there are wiring issues, yes, it will likely return.
Why does this code sometimes pair with SPN 2702?
SPN 2702 also relates to coolant temperature; they often point to similar sensor or circuit issues.
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