Overview

Code

Fault Code: 1894

PID: S27

SPN: 641

FMI: 9/9

LAMP: Amber

SRT: 

Reason

No communications on the J1939 data link between the engine ECM and the smart VGT controller.

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

The Engine Control Module (ECM) did not receive a valid J1939 data link message from the Variable Geometry Turbocharger (VGT) actuator for more than 1 second.

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.

VGT actuation will be disabled.

Exhaust gas recirculation (EGR) valve operation will be disabled.

Engine torque will be reduced if the engine is operated for an extended period of time with this fault active.

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

Possible causes of this fault code include:

The VGT actuator is not receiving power from the ECM. This can be caused by an open circuit in the power supply wire or low voltage supplied by the primary engine ECM.

• Rapid cycling of the keyswitch

An open return circuit on the VGT actuator circuit

An open or short circuit on the J1939 data link circuit between the ECM and VGT actuator

Intermittent communications between the VGT actuator and the primary engine ECM on the J1939 data link

A damaged termination resistor in the engine data link harness

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