What are the common causes of P1299?

Low engine coolant level. A thermostat that is stuck closed. A faulty cylinder head temperature sensor. An open or short in the cylinder head temperature sensor harness. A poor connection at the cylinder head temperature sensor connector.

Check the engine coolant level and look for leaks. Read the cylinder head temperature sensor on a scan tool. Test the thermostat and cooling fan operation. Inspect the cylinder head temperature sensor connector and wiring. Replace the sensor or thermostat if the overheat condition returns. Clear the code and retest.

P1299

Cylinder Head Overtemperature Protection Active

System: Injector circuits (P code)
Lamp: Check Engine Light
Category: Powertrain - Fuel/Air Metering

What it means

P1299 means Cylinder Head Overtemperature Protection Active.

Check these first

Low engine coolant level
A thermostat that is stuck closed
A faulty cylinder head temperature sensor
An open or short in the cylinder head temperature sensor harness
A poor connection at the cylinder head temperature sensor connector

What to do next

Check the engine coolant level and look for leaks
Read the cylinder head temperature sensor on a scan tool
Test the thermostat and cooling fan operation
Inspect the cylinder head temperature sensor connector and wiring
Replace the sensor or thermostat if the overheat condition returns
Clear the code and retest

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Updated

Generic SAE J2012 definition. Last updated 2026-10-10.