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P1299

Cylinder Head Overtemperature Protection Active.

  • Generic
  • Powertrain
  • Manufacturer code
  • High severity

How this code is built

P
SystemPowertrain
1
Defined byThe manufacturer
2
AreaFuel and air metering (injector circuit)
99
FaultThe specific fault in that area

What it means

P1299 is listed generically as Cylinder Head Overtemperature Protection Active. The engine control unit has seen cylinder head or coolant temperature rise above its limit and has switched on a protection strategy to limit heat and avoid damage. The exact strategy and trigger point depend on the manufacturer and engine, so check the model-specific data.

Symptoms

  • Engine temperature warning light or gauge reading high
  • Reduced power or the engine going into a limp or protection mode
  • Engine running rough or misfiring when hot
  • Some cylinders may be shut down, or the engine may run on a limited number of cylinders, on engines that use this protection
  • Coolant loss, steam or a smell of coolant
  • Cooling fans running constantly or at high speed

Possible causes

  • Low coolant level from a leak or poor bleeding after previous worklikely
  • Cooling system fault such as a stuck thermostat, failed water pump or blocked radiatorlikely
  • Cooling fan, fan relay or fan control circuit not workinglikely
  • Faulty cylinder head or coolant temperature sensor, or its wiring or connector, giving a false high readingpossible
  • Lean running or other combustion problem causing excess heatpossible
  • Head gasket failure or cracked head letting combustion gas into the coolantpossible
  • Restricted airflow through the radiator or condenser, such as debris or a damaged fan shroudrare

How to diagnose

  1. Read all stored and pending codes and the freeze frame data, noting coolant and cylinder head temperature, engine load and speed when the code set
  2. Check the coolant level only when the engine is cold, and look for external leaks, wet hoses and stains
  3. Inspect the cooling fans, relays, fuses and wiring, and check the fans switch on when the engine reaches temperature
  4. Inspect the temperature sensor connector and wiring for damage, corrosion or poor contact
  5. Compare the live temperature reading with an independent measurement of the actual engine temperature, to check the sensor is accurate
  6. Check the thermostat operation and that the upper and lower radiator hoses both get hot as the engine warms up
  7. Check for combustion gas in the coolant and pressure test the cooling system to look for head gasket problems
  8. Check the radiator and condenser for blockages and the water pump for proper circulation, following the model-specific procedure

How to fix

  • Repair any coolant leaks, then refill and bleed the system to the manufacturer's procedure
  • Replace a faulty thermostat, water pump or blocked radiator
  • Repair or replace faulty fans, relays or fan control wiring
  • Replace a faulty temperature sensor or repair its wiring and connector
  • Correct any lean running or combustion fault found
  • Repair the head gasket or cylinder head if combustion gas is leaking into the coolant

Can I keep driving?

High severity

Do not keep driving with this code active, because overheating can quickly cause serious engine damage. Stop safely, let the engine cool and have the cooling system checked before further use.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.

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