Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Pinpoint Test B: The Engine Overheats: Notes
The Engine Overheats
Normal Operation and Fault Conditions
The engine cooling system maintains the engine temperature during operation. Correct coolant flow through the engine, radiator and remainder of cooling system passages and components is essential to maintaining a correct engine temperature.
Engine coolant flows primarily from the engine to the radiator circuit and back to the coolant pump. Coolant is sent from the coolant pump through the engine block and cylinder heads. A separate circuit from the engine also feeds the heater core and turbochargers with coolant. The coolant pump circulates the coolant. The coolant thermostat is a control valve actuated by coolant temperature. When the thermostat is closed, coolant flow bypasses the radiator circuit and returns to the coolant pump. When the thermostat is opened, coolant flows through the radiator circuit to transfer engine-generated heat to the outside air.
Engine overheating generally occurs when there is a disruption in the ability to control either coolant flow at the correct rate, the inability to transfer heat from the engine through the coolant (including low coolant) or an inability to transfer engine-generated heat to the outside air through the radiator.
Possible Sources
- Low coolant level
- External engine coolant leak
- Airlock in system
- Pressure relief cap
- Restricted airflow through A/C condenser/radiator
- Internal engine coolant leak
- Transmission fluid warmer (if equipped)
- Turbochargers
- Coolant condition/concentration
- Non-OEM engine enhancement components
- Electric cooling fan
- CHT sensor
- ECT sensor
- Radiator
- Thermostat
- Temperature gauge
- Coolant pump
- Coolant flow restriction
- Active grill shudder
Diagnostic Trouble Code (DTC) Fault Trigger Conditions
| DTC | Description | Fault Trigger Conditions |
|---|---|---|
| P0217 | Engine Coolant Overtemperature Condition | Sets in the PCM when an engine overheat condition was sensed by the CHT sensor or the ECT sensor. |
| P1285 | Cylinder Head Overtemperature Condition | Sets in the PCM when an engine overheat condition was sensed by the CHT sensor or the ECT sensor. |
| P1299 | Cylinder Head Overtemperature Protection Active | Sets in the PCM when an engine overheat condition was sensed by the CHT sensor or the ECT sensor. A failure mode effects strategy called fail-safe cooling was activated to cool the engine. |
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.