Cummins fault code 6422
Engine Brake Actuator Driver Output 2 Circuit: circuit voltage low / shorted low
What it means
Cummins' description: Engine Brake Actuator Driver Output 2 Circuit - Voltage below normal, or shorted to low source.
SPN 1073 is Engine (Compression) Brake Output #2. FMI 4 means the voltage on the circuit is lower than possible for a good sensor, usually a short to ground, a damaged harness, or a failed sensor.
The engine (compression) brake and exhaust back pressure valve help slow the truck and warm up the engine and aftertreatment. The ECM controls them with solenoids and monitors their position.
What the lamp means
This code normally doesn't turn on a dash lamp. It's logged in the ECM for a technician to see, and often explains another active code.
Green, yellow, red: three ways this can look
The same code can be a quick fix or a reason to shut down. Match your situation to the closest example.
Keep an eye on it
A brake code that set once and the engine brake still works on all settings.
Schedule a repair
The engine brake doesn't work on one or more settings, or slow warm-up. Get it fixed. You're relying more on the service brakes.
Stop and get help
Back pressure valve stuck closed (big power loss, overheating exhaust), or no engine brake on steep grades with a heavy load. Don't haul heavy until it's repaired.
Common causes
FMI 4 is an electrical or signal fault, so start with the circuit:
- Engine brake solenoid circuit open or shorted
- Exhaust back pressure valve or position sensor fault
- Connector under the valve cover or at the exhaust damaged
If the circuit checks out, the reading may be real. Other possibilities: exhaust back pressure valve stuck from soot; engine brake out of adjustment.
What you can check before calling
- Test whether the engine brake works on each setting
- Listen for the back pressure valve moving at startup
- Look for damaged wiring near the exhaust
Clearing the code without fixing the cause usually brings it right back, and on emissions systems it can restart derate timers.
Engines and sources
Listed by Cummins for: QSB 6.7, QSL 9, QSX 15, QSB 4.5, QSF 3.8, QSG 12. Cummins uses the same fault code numbers across its electronic engines, including on-highway models like the ISB/B6.7, ISL/L9 and ISX/X15, though not every code applies to every engine or software level. Source: Cummins Tier 4 Fault Codes. Always confirm with Cummins service information (QuickServe) for your engine serial number.
Same SPN, other failure types
- 2363 SPN 1073 FMI 4
Engine Brake Actuator Driver Output 2 Circuit: circuit voltage low / shorted low - 2367 SPN 1073 FMI 3
Engine Brake Actuator Driver Output 2 Circuit: circuit voltage high / shorted high - 6421 SPN 1073 FMI 3
Engine Brake Actuator Driver Output 2 Circuit: circuit voltage high / shorted high
Related Engine brake and exhaust back pressure codes
- 6419 SPN 1072 FMI 4
Engine Brake Actuator Driver 1 Circuit: circuit voltage low / shorted low - 6418 SPN 1072 FMI 3
Engine Brake Actuator Driver 1 Circuit: circuit voltage high / shorted high - 5277 SPN 5626 FMI 13
Engine Exhaust Back Pressure Regulator: out of calibration - 5276 SPN 5625 FMI 4
Engine Exhaust Back Pressure Regulator Position Sensor Circuit: circuit voltage low / shorted low - 5275 SPN 5625 FMI 3
Engine Exhaust Back Pressure Regulator Position Sensor Circuit: circuit voltage high / shorted high - 5274 SPN 5625 FMI 2
Engine Exhaust Back Pressure Regulator Position: erratic or intermittent signal
Look up another code
Cummins fault code (like 1922), J1939 SPN and FMI (like SPN 3251 FMI 0), or an OBD-II code (like P0420).
Questions
What does Cummins fault code 6422 mean?
Cummins fault code 6422 is J1939 SPN 1073 FMI 4: Engine Brake Actuator Driver Output 2 Circuit - Voltage below normal, or shorted to low source. In plain terms: engine brake actuator driver output 2 circuit: circuit voltage low / shorted low.
Can I keep driving with Cummins code 6422?
Usually, yes. This code doesn't normally turn on a lamp by itself, but check for other active codes that might be more serious. Look at the green, yellow and red examples on this page to judge your situation.
What is the SPN and FMI for Cummins code 6422?
SPN 1073 identifies the part or system (Engine (Compression) Brake Output #2). FMI 4 describes the type of failure: circuit voltage low / shorted low.
What usually causes Cummins code 6422?
The most common causes are: engine brake solenoid circuit open or shorted; exhaust back pressure valve or position sensor fault; connector under the valve cover or at the exhaust damaged.
Diesel down in the Midlands?
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