Principles of Operation
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, operated by engine rotation through the accessory drive belt, 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.
The transmission cooler - warmer is mounted on the transmission. On initial startup, the transmission fluid heater coolant control valve opens and allows warm coolant from the engine to enter the transmission cooler - warmer to warm the transmission fluid. As the engine and transmission warm, the transmission fluid heater coolant control valve closes and the transmission fluid cooler coolant control valve opens, allowing cooler coolant from the radiator to enter the transmission cooler - warmer to cool the transmission fluid.
The degas bottle holds surplus coolant and removes air from the cooling system. It also allows for coolant expansion and system pressurization, replenishes coolant to the cooling system and serves as the location for service fill.
The cooling fan draws air through the radiator to help cool the system coolant as it passes through the radiator.
The thermostat monitor is a function of the PCM and is designed to verify correct thermostat operation. The PCM monitors the CHT sensor or ECT sensor (1.6L GTDI) and compares this value to an infered termperature model. The monitor executes once per drive cycle and has a monitor run duration of 300-800 seconds. If a malfunction occurs, DTC P0125 or P0128 sets, and the Malfunction Indicator Lamp (MIL) illuminates.
For engine specific information, refer to SPECIFICATIONS .
Normal Operation
The engine cooling system is a closed system providing for coolant expansion and contraction and also changes in pressure as coolant warms and cools with engine operation. Various gaskets, seals, hoses and clamps contain coolant within the cooling system and keep other fluids and contaminants from entering the cooling system.
Coolant loss can be attributed to either external or internal leaks anywhere within the cooling system.
For engine specific information, refer to SPECIFICATIONS .
The engine cooling system maintains engine temperatures during operation. Correct coolant flow through the engine, radiator and remainder of cooling system passages and components is essential to maintaining 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 with coolant and provides coolant flow to the transmission fluid heater coolant control valve. A circuit from the radiator provides coolant to the transmission fluid heater coolant control valve. For 1.6L GTDI and 2.0L GTDI engines, a circuit provides coolant flow to the turbocharger.
The coolant pump, operated by engine rotation through the accessory drive belt, 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 is allowed to flow through the radiator circuit in order 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 proper 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.
For engine specific information, refer to SPECIFICATIONS .
The 1.6L GTDI engine cooling system incorporates a engine coolant bypass valve and a heater shut-off valve. Using these two valves, the coolant flow through the engine block can be restricted or completely stagnated. The restriction or stagnation of the coolant flow makes it possible for the engine components to warm up faster during the warm-up phase. The heater shut-off valve is normally open and closes when energized to stagnate coolant flow throughout the cooling system if the engine coolant bypass is also closed. The heater shut-off valve blocks or allows coolant flow through the thermostat housing, coolant pump, engine block, heater core, turbocharger, transmission oil cooler, and engine oil cooler. The engine coolant bypass provides another coolant circuit for the engine block and is normally closed and opens when energized to provide coolant flow between the outlet of the engine block to the thermostat housing. The primary function of this valve is to increase coolant flow through the engine block reducing cooling system pressure and temperature fluctuations during high engine loads. If one or both valves do not open when commanded by the PCM an engine over temperature condition can result.
For more information, refer to PRINCIPLES OF OPERATION .
| DTC | Description | Fault Trigger Conditions |
|---|---|---|
| P0217 | Engine Coolant Overtemperature Condition | Indicates an engine overheat condition was sensed by the Cylinder Head Temperature (CHT) sensor. |
| P1285 | Cylinder Head Overtemperature Condition | Indicates an engine overheat condition was sensed by the cylinder head temperature CHT sensor. |
| P1299 | Cylinder Head Overtemperature Protection Active | Indicates an engine overheat condition was detected by the CHT sensor. A failure mode effects management strategy called fail-safe cooling was activated to cool the engine. |
DTC FAULT TRIGGER CONDITIONS
The engine cooling system maintains engine temperatures 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 with coolant and provides coolant flow to the transmission fluid heater coolant control valve. A circuit from the radiator provides coolant to the transmission fluid heater coolant control valve. For 1.6L GTDI and 2.0L GTDI engines, a circuit provides coolant flow to the turbocharger.
The coolant pump, operated by engine rotation through the accessory drive belt, 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 is allowed to flow through the radiator circuit in order to transfer engine-generated heat to the outside air.
Concerns of engine inability to reach normal operating temperature typically occur when the rate of coolant flow through some coolant circuits (radiator, bypass, heater core) is more than expected given the conditions. Heat is not allowed to build in the engine because a heat exchanger is removing too much heat, including the radiator, heater core and oil cooler. In addition, perceived concerns that the engine does not reach normal operating temperature can be related to a low coolant level or trapped air which does not allow for hot coolant to be available at the heater core, an inoperative climate control system, or for concerns perceived or related to an incorrect engine temperature gauge indication.
For engine specific information, refer to ENGINE COOLING .
The 1.6L GTDI engine cooling system incorporates a engine coolant bypass valve and a heater shut-off valve. Using these two valves, the coolant flow through the engine block can be restricted or completely stagnated. The restriction or stagnation of the coolant flow makes it possible for the engine components to warm up faster during the warm-up phase. The heater shut-off valve is normally open and closes when energized to stagnate coolant flow throughout the cooling system if the engine coolant bypass is closed. The heater shut-off valve blocks or allows coolant flow through the thermostat housing, coolant pump, engine block, heater core, turbocharger, transmission oil cooler, and engine oil cooler. The engine coolant bypass valve provides another coolant circuit for the engine block and is normally closed and opens when energized to provide coolant flow between the outlet of the engine block to the thermostat housing. The primary function of this valve is to increase coolant flow through the engine block reducing cooling system pressure and temperature fluctuations during high engine loads. The engine coolant bypass valve is commanded open during high engine temperatures to provide more cooling. If the engine coolant bypass valve mechanically sticks open the engine takes longer to reach operating temperature.
For more information, refer to PRINCIPLES OF OPERATION .
| DTC | Description | Fault Trigger Conditions |
|---|---|---|
| P0125 | Insufficient Coolant Temp for Closed Loop Fuel Control | Indicates the Cylinder Head Temperature (CHT) sensor or ECT sensor (1.6L GTDI) has not achieved the required temperature level to enter closed loop operating conditions within a specified amount of time after starting the engine. |
| P0128 | Coolant Temp Below Thermostat Regulating Temperature | Indicates that the thermostat monitor has not achieved the required engine operating temperature within a specified amount of time after starting the engine |
DTC FAULT TRIGGER CONDITIONS
The 1.6L GTDI engine cooling system incorporates a engine coolant bypass valve and a heater shut-off valve. Using these two valves, the coolant flow through the engine block can be restricted or completely stagnated. The restriction or stagnation of the coolant flow makes it possible for the engine components to warm up faster during the warm-up phase. Both solenoid valves are controlled by the PCM via a low side driver. The PCM monitors both solenoids for electrical faults and sets an appropriate DTC.
For more information, refer to PRINCIPLES OF OPERATION .
| DTC | Description | Fault Trigger Conditions |
|---|---|---|
| P26B7 | Engine Coolant Bypass Valve "C" Control Circuit/Open | The PCM monitors the Engine Coolant Bypass Valve "C" Control Circuit/Open circuit for high and low voltage. The test fails if the voltage exceeds a calibrated limit for a calibrated amount of time. |
DTC FAULT TRIGGER CONDITIONS
The 1.6L GTDI engine cooling system incorporates a engine coolant bypass valve and a heater shut-off valve. Using these two valves, the coolant flow through the engine block can be restricted or completely stagnated. The restriction or stagnation of the coolant flow makes it possible for the engine components to warm up faster during the warm-up phase. Both solenoid valves are controlled by the PCM via a low side driver. The PCM monitors both solenoids for electrical faults and sets an appropriate DTC.
For more information, refer to PRINCIPLES OF OPERATION .
| DTC | Description | Fault Trigger Conditions |
|---|---|---|
| P26BD | Engine Coolant Bypass Valve "D" Control Circuit/Open | The PCM monitors the Engine Coolant Bypass Valve "D" Control Circuit/Open circuit for high and low voltage. The test fails if the voltage exceeds a calibrated limit for a calibrated amount of time. |
DTC FAULT TRIGGER CONDITIONS