Base Engine Temperature - High
Engine temperature is higher than acceptable limits.
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What it means (plain English)
The engine's coolant temperature is running too high, which can lead to overheating.
What the computer is actually seeing
The Engine Control Module (ECM) monitors input from the coolant temperature sensor (CTS) and expects a normal range between 190°F to 220°F (88°C to 104°C).
What a healthy reading looks like
Coolant temperature should be between 190°F and 220°F (88°C to 104°C).
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; ensure it's at the proper level. If low, refill and check for leaks.
- 22. Inspect for any visible leaks in the coolant system (hoses, radiator, connections).
- 33. Connect a scan tool and check the live data for coolant temperature readings. It should match engine operating conditions.
- 44. If the temperature reading is too high (above 220°F / 104°C) while engine is running at normal operating conditions, proceed to the next step.
- 55. Check the CTS wiring for any damage or disconnection. Repair as necessary. If wiring is fine, go to step 6.
- 66. Test the CTS with a multimeter. At room temperature, it should read around 10k Ohms. If out of range, replace the sensor.
- 77. Inspect the thermostat; it should open fully when the engine reaches operating temp. If it appears stuck, replace it.
- 88. Finally, confirm the water pump is functioning. If it shows signs of failure, replace it.
Common causes
- Coolant level low or leaking
- Faulty coolant temperature sensor
- Thermostat stuck closed
- Cooling system blockage
- Failed water pump
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
No, high engine temperatures can cause severe engine damage if not addressed.
Will this code come back after clearing?
It can return if the underlying issue is not resolved.
Why does this code pair with SPN 1231?
SPN 1231 often indicates a direct issue with the coolant temperature sensor, which can cause misreadings.
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