P1299 Code: Cylinder Head Overtemperature Protection Active
⚠️ Severe · drivable
Drivable only briefly — the truck cuts power to protect the engine. Stop and let it cool, then fix the overheating cause.
What P1299 means
The cylinder head temperature sensor shows the engine is running too hot, so the computer has activated a protection mode that reduces power. The engine is being starved of fuel and power on purpose to keep it from destroying itself, and the overheating cause needs to be found.
Symptoms
- Check engine light on and reduced power
- Engine loses power under load
- Temperature gauge reading high
- Coolant leaking or low
- Cooling fan running constantly
Common causes
- most common: Low or leaking coolant
- common: Cooling fan not working
- common: Thermostat stuck closed
- less common: Clogged radiator or failed water pump
How to fix it
| Fix | DIY? | Typical cost |
|---|---|---|
| Check and top up the coolant level | Yes | $10–30 |
| Replace the thermostat | Yes | $20–60 |
| Repair the cooling fan or fan clutch | Mechanic | $200–500 |
| Find and repair the coolant leak | Mechanic | $100–500 |
Frequently asked questions
Can I drive with a P1299 code?
Only for a short time. The truck cuts power to protect the engine. Stop, let it cool, and find the overheating cause before driving more.
Why does my truck lose power with P1299?
The computer deliberately reduces fuel and power when the cylinder head gets too hot, to protect the engine from serious damage.
How much does it cost to fix P1299?
A thermostat is $20–$60 as a DIY job. A cooling fan repair is $200–$500, and leak repairs vary by location.
Related codes
P1285
P1285 Code: Cylinder Head Temperature Sensor Circuit Excessive Time to Closed Loop
P0117P0117 Code: Engine Coolant Temperature Circuit Low Input
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.