Cummins ISX15 CM2250 (2010-12) Fault Code: 6421 PID: SID 254 SPN: 1073 FMI: 3 Engine Brake Actuator Driver Output 2 Circuit- Voltage Above Normal or Shorted to High Source

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 ECM detected the engine brake 2 PWM signal was detected to be system voltage when the PWM signal was turned OFF.

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 INSITE? electronic service tool will change to INACTIVE immediately after 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
Possible causes of this fault code include:

A short circuit to battery in the engine harness.
A malfunctioning engine brake solenoid.

Possible Cause:
1) Engine Harness
2) Engine Brake Solenoid failure
3) ECM failure