P0116 - Engine Coolant Temperature Sensor Performance
Theory of Operation
The Engine Coolant Temperature Sensor (ECT) is located near the thermostat housing and is used to measure the engine coolant temperature. The Engine Coolant Temperature Sensor receives 5-Volts and a sensor ground from the PCM. The PCM monitors the change in voltage to determine the coolant temperature. There are two parts to this fault code, a key on check and a rationality check. After an eight hour cold soak, at key on the readings for the Inlet Air Temperature, Intake Air Temperature and Engine Coolant Temperature Sensors are all compared. If the temperatures differ more than a calibrated amount, then the appropriate sensor fault code would be recorded. The key on monitor is disabled for ambient temperatures below 20°F. This monitor looks for all the sensors to be grouped on one temperature or, in the case that the monitor fails, two sensors grouped at one temperature and one outlier. In the case that all three sensor values are distributed over a range of temperatures this diagnostic will not run. A block heater is one possible cause of such a distribution. The PCM rationality check looks at the temperature reading from the sensor over time and ensures that it changes with engine running. If the sensor reading does not change over a calibrated time limit, the fault will be recorded. Both the key-on and rationality portions of this monitor require that the diagnostic fails in two consecutive drive cycles before the MIL lamp is lit. The ETC lamp will also be illuminated. During this time the PCM uses a default value for the Coolant Temperature Sensor. The PCM turns off the MIL lamp when the
diagnostic runs and passes in four consecutive drive cycles.
When Monitored and Set Conditions
When Monitored: This diagnostic runs continuously when the following conditions are met:
• With the Engine running.
Set Conditions:
• The Powertrain Control Module (PCM) does not read a change in value from the Engine Coolant Temperature (ECT) Sensor over a calibrated amount of time.
Default Actions:
• The MIL is illuminated.
Possible Causes
LOW COOLANT LEVEL
ENGINE COOLANT TEMPERATURE (ECT) SENSOR
THERMOSTAT
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTCBased Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
1. CHECK THE COOLANT LEVEL
1. Turn the ignition off.
2. With the engine cold, verify the level of coolant in the cooling system.
Is the cooling system full of coolant?
Yes
• Go To 2
No
• Fill the cooling system to the proper level.
• Perform the POWERTRAIN VERIFICATION TEST - 6.7L. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
2. THERMOSTAT
1. With the scan tool, check DTCs.
NOTE: If DTC P0117 or P0118 are present, repair those DTCs before proceeding with this test.
Is DTC P0128-Thermostat Rationality present?
Yes
• Replace the Thermostat in accordance with the Service Information..(Refer to 07 - Cooling/Engine/THERMOSTAT/Removal)
• Perform the POWERTRAIN VERIFICATION TEST - 6.7L. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
No
• Go To 3
3. COOLANT TEMPERATURE SENSOR
1. Remove the Coolant Temperature Sensor and reconnect the wiring to the sensor.
2. Turn the ignition on.
3. Monitor scan tool while heating the sensor with an external heat source (DO NOT USE OPEN FLAME).
Does the reading from the Coolant Temperature Sensor increase at least 5°F on the scan tool?
Yes
• Go To 4
No
• Replace the 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).
4. COOLANT TEMPERATURE SENSOR
1. Let vehicle cold soak for eight hours.
2. Turn the ignition on.
3. With a scan tool, monitor Inlet Air Temperature, EGR Temperature and Coolant Temperature Sensors.
NOTE: Make sure the Ambient Air Temperature is above 20°F.
NOTE: Make sure there is no external heat source, such as a block heater, operating during this test or within the 8 hour cold soak.
Does the Coolant Temperature Sensor read more than a 18°F (10°C) above or below the other sensors?
Yes
• Replace the 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).
No
• Perform the INTERMITTENT CONDITION diagnostic procedure. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).