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 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. 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 coolant pump, operated by engine rotation through a sprocket which is driven by the timing chain, 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.
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 the fan clutch is always engaged. 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 Description and Operation in the Description and Operation information.
- DTC P0125 Insufficient Coolant Temperature For Closed Loop Fuel Control
- DTC P0126 Insufficient Coolant Temperature For Stable Operation
- DTC P0128 Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)
This pinpoint test is intended to diagnose the following:
- Low coolant level
- Thermostat
- Engine Coolant Temperature (ECT) 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.
-------------------------------------------------
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 .
-------------------------------------------------
C2 CHECK FOR DTC P0125, P0126 or P0128
- 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 ECT gauge is suspected, CHECK the ECT gauge operation. REFER to Instrumentation, Message Center, and Warning Chimes Instrumentation, Message Center and Warning Chimes. If an inoperative climate control system is suspected, CHECK the climate control system operation. REFER to Climate Control System - General Information and Diagnostics Climate Control System. If any other PCM DTCs are retrieved, REFER to Electronic Engine Controls P Codes for Electronic Engine Controls.
-------------------------------------------------
C3 CHECK THE COOLING FAN OPERATION
- Carry out the cooling fan clutch component tests. Refer to Component Tests. Fan Clutch Test
- Is the cooling fan clutch OK?
Yes
GO to C4.
No
INSTALL a new cooling fan clutch. TEST the system for normal operation.
-------------------------------------------------
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
-------------------------------------------------