Cummins ISB4.5 CM2150 Fault Code: 1938 PID: 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 control module (ECM). The VGT actuator performs its own diagnostics and reports errors back to the primary engine 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 500 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 ECM will turn off the amber CHECK ENGINE lamp immediately after the voltage to the VGT actuator is greater than +10-VDC and the engine speed is zero rpm or greater than 500 rpm.
-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
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.