Pinpoint Test C: The Engine Does Not Reach Normal Operating Temperature
Engine Cooling
Pinpoint Tests
Pinpoint Test C: The Engine Does Not Reach Normal Operating Temperature
Normal Operation
The engine cooling system functions to maintain 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. From the coolant pump, coolant is sent through the engine block and cylinder heads. A separate circuit from the engine also feeds the heater core with coolant. The 2.5L engine coolant pump is operated by engine rotation through a pulley driven by the accessory drive belt. The 3.0L coolant pump is operated by a V-ribbed belt driven by a pulley attached to the camshaft. The 3.5L coolant pump is operated through a sprocket driven by the timing chain. 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, heater core) is more than expected given the conditions, or when the electric cooling fans operate all the time. 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 vehicle/engine specific information, refer to Engine Cooling Description and Operation in the Description and Operation portion.
- DTC P0125 - Insufficient Coolant Temp for Closed Loop Fuel Control
- DTC P0128 - Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temperature)
This pinpoint test is intended to diagnose the following:
- Low coolant level
- Thermostat
- Engine Coolant Temperature (ECT) indicator system (gauge)
- Engine cooling fan
PINPOINT TEST C: THE ENGINE DOES NOT REACH NORMAL OPERATING TEMPERATURE
WARNING: Always allow the engine to cool before opening the cooling system. Do not unscrew the coolant pressure relief cap when the engine is operating or the cooling system is hot. The cooling system is under pressure; steam and hot liquid can come out forcefully when the cap is loosened slightly. Failure to follow these instructions may result in serious personal injury.
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C1 CARRY OUT INSPECTION AND VERIFICATION
- Carry out the Inspection and Verification procedure. Inspection and Verification
- Were any concerns found?
Yes
REPAIR as needed. TEST the system for normal operation.
No
GO to C2.
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C2 CHECK FOR DTC P0125 or P0128
NOTE: Refer to Computers and Control Systems Information for correct scan tool hook-up procedure.
- Check for DTC P0125 or P0128.
- Is DTC P0125 or P0128 present?
Yes
GO to C3.
No
The cooling system is operational. If an inoperative engine coolant temperature gauge is suspected, CHECK the engine coolant temperature gauge operation. REFER to Instrument Panel, Gauges and Warning Indicators. If an inoperative climate control system is suspected, CHECK the climate control system operation. If any other DTCs are retrieved, REFER to Computers and Control Systems Information.
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C3 CHECK THE ELECTRIC COOLING FAN OPERATION
- Allow the engine to cool.
- Make sure the A/C switch is OFF (if equipped).
- Start the engine.
- Check the electric cooling fan.
- Is the electric cooling fan on all the time?
Yes
DIAGNOSE the electric cooling fan operation. REFER to Computers and Control Systems Information.
No
GO to C4.
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C4 CHECK THE COOLANT LEVEL
- NOTE: Allow the engine to cool before checking the coolant level.
- Visually check the engine coolant level in the degas bottle.
- Is the engine coolant level within specification?
Yes
INSTALL a new thermostat. TEST the system for normal operation.
No
GO to Pinpoint Test A to diagnose a coolant leak. Pinpoint Test A: Loss Of Coolant
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