Diagnostic Routine C

Diagnostic Routine C

Diagnostic Overview

The Engine Does Not Reach Normal Operating Temperature

Normal Operation and Fault Conditions

The engine cooling system maintains 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 with coolant. The coolant pump circulates the coolant. For 2.0L GTDI (Gasoline Turbocharged Direct Injection), the coolant pump is operated by engine rotation through a pulley driven by the accessory drive belt. For 3.5L Ti-VCT (Twin Independent Variable Cam Timing), the coolant pump is operated by engine rotation through a sprocket driven by the camshaft 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 flows 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 fan operates all of 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. The engine not reaching normal operating temperature can be attributed to:
- Low coolant level
- Thermostat
- Engine cooling fan always on
- Temperature gauge

Engine Cooling

DTC Fault Trigger Conditions






Pinpoint Test

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.

1. CARRY OUT INSPECTION AND VERIFICATION

1. Carry out Inspection and Verification. REFER to Symptom Chart: Engine Cooling Symptom Related Diagnostic Procedures.

Were any concerns found?






2. CHECK FOR DTC (Diagnostic Trouble Code) P0125 or P0128

1. Check for DTC (Diagnostic Trouble Code) P0125 or P0128.

Is DTC (Diagnostic Trouble Code) P0125 or P0128 present?






3. CHECK THE ELECTRIC COOLING FAN OPERATION

1. Allow the engine to cool.

2. Make sure the A/C (Air Conditioning) switch is OFF.

3. Start the engine.

4. Check the electric cooling fan.

Is the electric cooling fan on all the time?






4. CHECK THE COOLANT LEVEL

NOTE: Allow the engine to cool before checking the coolant level.

1. Visually check the engine coolant level in the coolant expansion tank.

Is the engine coolant level within specification?