What Does P1304 Mean?
P1304 indicates that the engine control module has activated cylinder head overtemperature protection to prevent catastrophic engine damage. This mode typically reduces power output, retards timing, or enriches the fuel mixture to lower combustion temperatures. The protection system engages when cylinder head temperatures exceed safe thresholds, often due to cooling system failures or extreme operating conditions.
Safety Warning
Continued driving with overtemperature protection active risks cylinder head warping, head gasket failure, or complete engine seizure. Pull over and allow the engine to cool immediately.
Common Causes
30%
Low coolant level or coolant leak
25%
Failed or stuck thermostat
20%
Malfunctioning water pump
15%
Clogged or damaged radiator
10%
Faulty cylinder head temperature sensor
Diagnostic Steps
1
Check coolant level and inspect for visible leaks in hoses, radiator, and water pump weep hole.
2
Monitor cylinder head temperature with live data to verify the sensor is reading accurately compared to an infrared thermometer.
3
Test thermostat operation by observing temperature rise pattern during warm-up — it should open at the rated temperature.
4
Inspect the radiator for blockages, bent fins, or debris restricting airflow.
5
Verify water pump operation by checking for adequate coolant flow with the radiator cap removed at idle.
6
Perform a cooling system pressure test to identify any hidden leaks.
Estimated Repair Cost
$150 - $900
Parts + labor, varies by vehicle and location
P1304 indicates that the engine control module has activated cylinder head overtemperature protection to prevent catastrophic engine damage. This mode typically reduces power output, retards timing, or enriches the fuel mixture to lower combustion temperatures. The protection system engages when cyl...
The most common cause of P1304 (Cylinder Head Overtemperature Protection Active) is: Low coolant level or coolant leak
Typical repair costs for P1304 range from $150 to $900, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Continued driving with overtemperature protection active risks cylinder head warping, head gasket failure, or complete engine seizure. Pull over and allow the engine to cool immediately.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1304 to identify the root cause.
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Quick Info
Category
Powertrain
System
Engine Cooling / Thermal Management
Difficulty
Type
Manufacturer
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