Engine Coolant Temperature Too High
The engine coolant temperature is exceeding normal operating levels.
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What it means (plain English)
The engine is overheating, which means the coolant temperature is higher than 240°F (115°C). This could damage the engine.
What the computer is actually seeing
The Engine Control Unit (ECU) is reading coolant temperatures from the sensor that are consistently above 240°F (115°C), triggering the fault code SPN 1926.
What a healthy reading looks like
Normal coolant temperature is typically around 195°F to 215°F (90°C to 102°C). Over 240°F (115°C) is considered too high.
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 coolant level in the reservoir and radiator; top off if low (expected level: full). Decision: If low, refill and monitor for leaks.
- 22. Inspect coolant hoses for leaks or blockages. Decision: If damaged, replace hoses and recheck temp. If not, continue.
- 33. Test the thermostat by removing and boiling it in water; it should open at around 195°F to 200°F (90°C to 93°C). Decision: If it doesn't open, replace the thermostat.
- 44. Check the operation of the water pump; look for leaks or improper circulation (feeling hoses). Decision: If pump isn't circulating, replace it.
- 55. Check the radiator for clogs or debris; make sure it's clean and airflow is unobstructed. Decision: If clogged, clean or replace the radiator.
- 66. Test the coolant temperature sensor with a multimeter; expected resistance should change with temperature (about 2500 ohms at 80°F). Decision: If it reads incorrectly, replace the sensor.
Common causes
- Low coolant level
- Thermostat stuck closed
- Failed water pump
- Radiator blockage
- Faulty coolant temperature sensor
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
No, it's not safe to drive because overheating can cause severe engine damage.
Will this code come back after fixing?
It shouldn't if all issues causing the overheating are resolved.
Why do I see this with SPN 1908?
SPN 1908 often relates to the coolant temperature sensor; both codes can trigger due to overheating conditions.
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