P0217 - Coolant Temperature Too High
Theory of Operation
The Coolant Temperature Sensor is a variable resistor sensor and is used to measure the temperature of the coolant of the engine. The PCM supplies 5-Volts to the Engine Coolant Temperature Sensor (ECT) Signal circuit. The PCM monitors the change in voltage caused by changes in the resistance of the sensor to determine the coolant temperature. The engine coolant temperature value is used by the PCM for the engine protection system and engine emissions control. The Engine Coolant Temperature Sensor is located near the thermostat housing. This fault becomes active when the PCM detects a coolant temperature higher than a calibrated limit for a calibrated amount of time. The PCM illuminates the MIL lamp after the diagnostic runs and fails once. During this time the customer may experience an engine power derate, and regeneration mode will be disabled. The PCM will turn off the MIL lamp after the diagnostic runs and passes in four consecutive drive cycles.
When Monitored:
While the engine is running.
Set Condition:
The engine coolant temperature is above a calibrated value for a calibrated amount of time.
Possible Causes
COOLING SYSTEM FAILURE
ECT SENSOR
MECHANICAL FAILURE
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTC- Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
1. COOLING SYSTEM FAILURE
NOTE: If other cooling system DTCs are present, repair those DTCs before proceeding.
1. Check the engine cooling system operation. Refer to cooling, Diagnosis and Testing, Preliminary check.
(Refer to 07 - Cooling - Diagnosis and Testing) . Is the Cooling system operating normally?
Yes
Go To 2
No
Repair the cooling system failure.
Perform the POWERTRAIN VERIFICATION TEST - 6.7L. (Refer to 28 - DTC-Based
Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
2. CHECK THE ECT SENSOR
1. Allow the engine to reach normal operating temperature.
2. Use a temperature probe and measure the engine temperature near the ECT Sensor.
3. With the scan tool, read the Engine Coolant Temperature.
4. Compare the temperature probe reading with the scan tool reading.
Are the readings within 10°F of each other?
Yes
Repair the cause of mechanical failure.
Perform the POWERTRAIN VERIFICATION TEST - 6.7L. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
No
Replace the Engine Coolant Temperature Sensor in accordance with the Service Information.(Refer to 07 - Cooling/Engine/SENSOR, Coolant Temperature/Removal)
Perform the POWERTRAIN VERIFICATION TEST - 6.7L. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).