Cummins ISB4.5 CM2150 Fault Code: 334 PID: 116 SPN: 110 FMI: 2 Engine Coolant Temperature – Data Erratic Intermittent or Incorrect.

Circuit Description
The engine coolant temperature sensor is used by the electronic control module (ECM) to monitor the engine coolant temperature. The ECM monitors the voltage on the signal pin and converts this to a temperature value. The engine coolant temperature value is used by the ECM for the engine protection system and engine emission control.

Component Location
The engine coolant temperature sensor is located on the thermostat housing.

Conditions for Running the Diagnostics
The engine must be turned off for period of 8 hours before this diagnostic will run. This diagnostic runs when the keyswitch is turned to the ON position after an 8 hour cold soak.

Conditions for Setting the Fault Codes
If coolant temperature is found to be higher than intake manifold temperature by a calibratable value, the fault code is logged. The diagnostic also checks to make sure that coolant temperature increases during the first 10 minutes of engine operation. If coolant temperature does not increase by a calibratable value, this fault code is logged.

Action Taken When the Fault Code is Active
-The ECM will estimate engine coolant temperature.
-An engine torque derate will be activated after 36 hours of engine operation with the fault code active.
-The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
-The ECM illminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

Conditions for Clearing the Fault Code
-To validate the repair, start the engine and let it idle for 1 minute.
-The ECM will turn off the amber CHECK ENGINE light immediately after the diagnostic runs and passes.
-The ECM will turn off the MIL after 3 consecutive ignition cycles that the diagnostic runs and passes.
-This fault code and MIL can also be cleared with INSITE™ electronic service tool.

Shop Talk
Two different failure modes of the engine coolant temperature sensor can trigger this fault code. The engine must be turned off for period of 8 hours before this diagnostic will run. When the keyswitch is turned ON after an 8 hour cold soak, engine coolant temperature is compared to intake manifold temperature. If coolant temperature is found to be higher than intake manifold temperature by a calibratable value, the fault code is logged. The diagnostic also checks to make sure that coolant temperature increases during the first 10 minutes of engine operation. If coolant temperature does not increase by a calibratable value, this fault code is logged.

Possible Causes
-Stuck in-range engine coolant temperature sensor.
-High resistance in the engine coolant temperature sensor signal or return lines.