Overview

Code

Fault Code: 1938

PID: S212

SPN: 3597

FMI: 1/18

LAMP: Amber

SRT:    

Reason

Low battery voltage detected by the VGT actuator.

Effect

Possible reduced engine performance.

VGT Actuator Circuit

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 malfunctions back to the primary engine ECM, using the J1939 data link. The ECM then decodes the error message and converts it to a fault code.

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 or when the engine is running.

Conditions for Setting the Fault Codes

Voltage supplied to the Variable Geometry Turbocharger (VGT) actuator dropped below 10-VDC for 10 seconds and the engine speed was at zero rpm or greater than 575 rpm.

Action Taken When the Fault Code is Active

• The ECM illuminates the amber CHECK ENGINE lamp and/or the malfunction indicator lamp (MIL) immediately when the diagnostic runs and fails.

Conditions for Clearing the Fault Code

• To validate the repair, perform a key cycle, start the engine and let it idle for 1 minute.
• The fault code status displayed by the recommended Cummins electronic service tool or equivalent will change to INACTIVE immediately after the diagnostic runs and passes.
• The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
• For On-Board Diagnostics (OBD) engines, the ECM will extinguish the Malfunction Indicator Lamp (MIL) after three consecutive trips where the diagnostic runs and passes.
• The “Reset All Faults” command in the recommended Cummins electronic service tool or equivalent 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. 

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