Cooling System Temperature Sensor Circuit Low Input
The ECM detects a low voltage signal from the cooling temperature sensor.
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What it means (plain English)
The cooling system temperature sensor is sending a signal that says the engine is colder than it really is, usually below 0.5 volts when it should be much higher.
What the computer is actually seeing
The engine control module (ECM) monitors the voltage from the cooling temperature sensor. If it sees a voltage below 0.5 volts when the engine is at operating temperature, it triggers this code.
What a healthy reading looks like
A properly functioning cooling temperature sensor should show a range between 0.5 and 4.5 volts at normal operating temperatures (185°F to 212°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 cooling system fluid level. Ensure it is at the proper level before diagnosing further.
- 2Inspect wiring and connectors leading to the cooling temperature sensor for corrosion or damage. Repair as needed.
- 3Using a multimeter, measure the voltage at the sensor connector while the engine is running. It should read between 0.5 and 4.5 volts.
- 4If the voltage is below 0.5 volts, replace the cooling temperature sensor and retest.
- 5If the voltage is good and the wiring is intact, check for ECM updates or faults.
Common causes
- Faulty cooling temperature sensor
- Wiring or connector issues
- Corrosion or shorts in the sensor circuit
- ECM software issues
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's moderate severity; the vehicle may run poorly and could affect engine temperature management, so drive cautiously.
Will this code come back after clearing?
If the underlying issue isn't fixed, yes, it will likely return.
Why does this code appear with other SPN codes?
Related codes may indicate other temperature sensor or circuit issues that can compound the problem.
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