Cummins Fault Code 6422

12/12/2025

Overview

CODE

REASON

EFFECT

Fault Code: 6422
PID:
SPN: 1073
FMI: 4/4
LAMP: None
SRT:

Low voltage detected at the engine brake solenoid number 2 signal circuit.

Possible reduce engine braking performance.

Cummins Fault Code 6422 — Engine Brake Actuator Driver 2 Circuit

Circuit Description

The engine control module (ECM) controls engine brakes on cylinders 4, 5, and 6 by sending a signal on the engine brake solenoid number 2 signal circuit. If an engine brake is installed, there will be a jumper harness from this connector to the engine brake pass-through connectors on the rocker lever housing.

Component Location

The engine brake solenoids are located under the valve cover. The engine brake solenoids are controlled through the engine harness by the ECM.

Conditions for Running the Diagnostics

This diagnostic runs when the keyswitch is in the ON position and when the pulse width modulated (PWM) device is getting energized or de-energized. In some cases, the diagnostics can also run at some fixed intervals.

Conditions for Setting the Fault Codes

The Engine Control Module (ECM) detected the engine brake 2 pulse width modulated (PWM) signal was not detected to be system voltage when the PWM signal was turned on.

Action Taken When the Fault Code is Active

The ECM logs the fault code immediately when the diagnostic runs and fails.

The engine brake 2 circuit will be disabled.

Conditions for Clearing the Fault Code

To validate the repair, drive the vehicle and operate the engine brakes. This will allow the diagnostic to run. If the fault code does not become active again, the repair has been validated.
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 “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.