Engine Coolant Temperature Sensor 1 Circuit Low
The engine coolant temperature sensor circuit is reading a low voltage.
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 uses a sensor to read how hot the coolant is. If it sees a voltage drop below about 0.1 volts, it thinks the engine is too cool, which can mess up fuel calculations.
What the computer is actually seeing
The engine control module (ECM) sees a voltage drop from the coolant temperature sensor that is lower than the normal operating range, which is typically 0.5 to 4.5 volts depending on the temperature.
What a healthy reading looks like
Normal voltage from a functioning coolant temperature sensor should be between 0.5V (cold) and 4.5V (hot).
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 and not leaking. If low, refill and monitor for leaks.
- 22. Inspect the wiring and connectors to the coolant temperature sensor for any physical damage or corrosion. Repair if found.
- 33. Use a multimeter to measure the voltage from the coolant temperature sensor while the engine is running. Expected range is 0.5V to 4.5V. If below 0.1V, proceed to next step.
- 44. Disconnect the coolant temperature sensor connector and check the resistance across the sensor terminals. It should change based on temperature. If resistance is out of spec, replace the sensor.
- 55. If the sensor is within spec but voltage is still low, check the ECM for faults, and ensure it's functioning properly.
Common causes
- Faulty coolant temperature sensor
- Wiring damage or corrosion
- Poor connector contacts
- Coolant leaks affecting sensor immersion
Typical repair cost
$$ - $$
Related codes
Frequently asked questions
Is it safe to drive with this code present?
It's generally safe to drive, but fuel efficiency and emissions may be impacted. Monitor engine temperature closely.
Will this code come back after clearing it?
If the underlying issue isn't fixed, the code is likely to return shortly after clearing it.
Why does this code activate with other coolant related codes?
Multiple coolant sensors may function in conjunction, and issues with one can influence readings of others.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
Start guided diagnostic →