Cooling System Temperature Sensor Circuit Low
Indicates a low voltage from the cooling system temperature sensor.
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What it means (plain English)
The cooling system temperature sensor is sending low voltage readings to the computer, which means it thinks the engine is cooler than it actually is, potentially leading to incorrect engine operation.
What the computer is actually seeing
The Engine Control Module (ECM) is monitoring the cooling system temperature sensor input. If the voltage drops below about 0.1 volts, it triggers SPN 2373.
What a healthy reading looks like
The cooling system temperature sensor should typically output between 0.5 to 4.5 volts, depending on coolant temperature (approximately 0 degrees Celsius = 4.5V, 100 degrees Celsius = 0.5V).
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. It should be at the proper level according to the manufacturer's specifications.
- 22. Inspect the wiring and connectors to the coolant temperature sensor for any damage, corrosion, or loose connections.
- 33. Measure the voltage at the coolant temperature sensor connector with the engine running. It should be between 0.5 to 4.5 volts based on the engine temperature.
- 44. If voltage is low, replace the coolant temperature sensor and retest.
- 55. If voltage is normal, check for continuity back to the ECM, looking for any breaks or shorts in the wiring.
- 66. If wiring is okay, consider replacing the ECM.
Common causes
- Faulty coolant temperature sensor
- Faulty wiring or connector
- Corrosion or poor contact in the electrical connector
- Low coolant level
- ECM malfunction
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's moderate severity; you may be able to drive, but performance may suffer, and it can negatively affect emissions.
Will this code come back after clearing it?
If the issue causing the low voltage isn’t fixed, the code will likely reappear.
Why does this code pair with other codes?
Codes like SPN 190 or SPN 192 relate to engine temperature and can indicate multiple failures in the cooling system.
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