Coolant Level Low
The engine coolant level is below the required threshold.
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What it means (plain English)
The engine's computer is checking the coolant level, and it sees that it's too low, possibly risking overheating.
What the computer is actually seeing
The module reads the coolant level sensor input voltage; normally it should be between 0.5V (high) and 4.5V (low) under correct conditions. A voltage below 0.5V indicates low coolant.
What a healthy reading looks like
Expected sensor voltage should be between 0.5V to 4.5V. Coolant temperature should be within 70°C to 110°C under operating conditions.
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. Inspect the coolant reservoir for proper fluid level; fill to the full mark if low.
- 22. Check for any leaks in hoses, radiator, or water pump.
- 33. Test the coolant level sensor's electrical connection, ensuring no corrosion or damage.
- 44. With the engine running, measure the voltage at the coolant level sensor. Is it between 0.5V and 4.5V? If it's low, replace the sensor and retest.
- 55. If voltage is normal, but coolant is still low, inspect the system for leaks or other issues.
Common causes
- Low coolant level due to leaks
- Faulty coolant level sensor
- Wiring issues or connector corrosion
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code active?
It's moderate severity; address it soon, but it's generally drivable unless you notice overheating.
Will this code return after fixing?
If you properly resolve the low coolant issue and replace the sensor if faulty, it should not come back.
Why does this code show up with SPN 6780?
SPN 6780 indicates coolant temperature too high, which can happen if the level is low, causing overheating.
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