P1299

Symptoms

• Check engine light on
• engine overheat alert on the dash
• cooling fan running at high speed
• engine suddenly running very rough (cylinders deactivated by the protection strategy)
• limp mode with severely limited speed
• A/C deactivated.

Probable causes

• 1) Low or lost engine coolant. 2) Defective thermostat. 3) Defective cylinder head temperature (CHT) sensor. 4) Water pump problems. 5) Insufficient airflow through the radiator. 6) Wiring/connector issues or open circuits in the CHT sensor circuit. 7) Exceeding towing or load-carrying capacity. In general
• any failure of a component that controls or monitors engine cooling/temperature can set or contribute to this code.

Diagnostic steps

1. Treat this as an active overheating event — do not continue driving until the cause is found; the protection strategy exists to prevent engine damage.
2. Let the engine cool, then check coolant level and inspect for leaks; correct low coolant first.
3. Inspect the radiator for blocked airflow and verify cooling fan operation.
4. Test the thermostat for correct opening.
5. Check the CHT sensor and its wiring/connectors for defects or open circuits; compare its reading against actual engine temperature.
6. Verify water pump operation and coolant circulation.
7. Consider operating conditions (towing/overloading) as a contributing factor.
8. After repair, clear the code and confirm normal operating temperature on a road test.