Low Coolant Level
Indicates that the coolant level in the reservoir is below the minimum threshold.
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 system is seeing that the coolant level is too low, which could cause overheating. Campain the coolant reservoir, if it hits the minimum level, this warning lights up.
What the computer is actually seeing
The engine control unit (ECU) monitors coolant level via a sensor in the reservoir. When the sensor detects less than 0.5 volts (indicating low coolant), it triggers the SPN 1673 code.
What a healthy reading looks like
Coolant level should register above the minimum line in the reservoir when the engine is cold. Voltage from the coolant level sensor should typically be between 0.5 to 5 volts, depending on level.
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 in the reservoir; if it's below the minimum, add coolant and see if code returns.
- 22. Inspect for visible leaks in hoses, radiator, and engine; repair any leaks found.
- 33. Test the coolant level sensor: Disconnect the connector and measure the voltage when coolant is at min/max level; it should change from 0.5V (low) to 5V (high). If it doesn't, replace the sensor.
- 44. Check wiring from sensor to ECU for continuity and shorts; repair as necessary; retest.
Common causes
- Low coolant due to leaks
- Faulty coolant level sensor
- Wiring issues to the coolant level sensor
- Engine overheating due to low levels
Typical repair cost
$100-$300
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's generally not safe; low coolant can cause overheating.
Will the code come back after clearing?
If the underlying issue isn't resolved, yes, it will come back.
Why do I get this with SPN 1674?
Both relate to coolant level; SPN 1674 may indicate a different fault in the cooling system.
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