Cummins ISX12 CM2250 (2010-12) Fault Code: 1938 PID: SID 212 SPN: 3597 FMI: 18 ECU Power Output Supply Voltage 1- Data Valid but Below Normal Operating Range- Moderately Severe Level

Circuit Description
The variable geometry turbocharger (VGT) is electronically activated by the VGT actuator. The VGT actuator is a smart device and receives information via the J1939 data link from the primary engine ECM. The VGT actuator performs its own diagnostics and reports malfunctions back to the primary engine electronic control module (ECM) using the J1939 data link.

Component Location
The VGT actuator is located on the turbocharger bearing housing.

Conditions for Running the Diagnostics
This diagnostic runs continuously when the keyswitch is in the ON position.

Conditions for Setting the Fault Codes
The fault code is set when the voltage supplied to the VGT actuator drops below 10-VDC for 10 seconds and the engine speed must be zero rpm or above 575 rpm.

Action Taken When the Fault Code is Active
The ECM illuminates the amber CHECK ENGINE lamp and/or Malfunction Indicator Lamp (MIL) immediately when the diagnostic runs and fails.
The VGT actuation will continue until battery voltage drops low enough that VGT actuation can not continue.
Conditions for Clearing the Fault Code
To validate the repair, start the engine and let it idle for 1 minute.
The fault code status displayed by INSITE? electronic service tool will change to INACTIVE immediately after the voltage to the VGT actuator is greater than 10-VDC, the engine speed is zero or greater than 575 rpm, and the diagnostic runs and passes.
The ECM will turn off the amber CHECK ENGINE lamp after the diagnostic runs and passes.
For On-Board Diagnostic (OBD) engines, the ECM will turn off the MIL after three consecutive trips where the diagnostic runs and passes.
The ?Reset All Faults? command in INSITE? electronic service tool can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications

Shop Talk
This fault code is logged when the voltage to the VGT actuator drops below 10-VDC. The VGT will still continue to respond to commands from the primary engine ECM

Possible Cause:
1) Battery failure
2) ECM failure