Cummins fault code 556
Crankcase Pressure: reading above normal (most severe)
What it means
Cummins' description: Crankcase Pressure - Data valid but above normal operational range - Most Severe Level.
SPN 101 is Engine Crankcase Pressure. FMI 0 means the sensor is working, but the value it reports is far above where it should be. This is the most severe 'high' level.
The crankcase ventilation system relieves pressure from blow-by gases. The ECM monitors crankcase pressure, and some systems have a heated breather to keep it from freezing.
What the lamp means
A red stop lamp means Cummins treats this as serious. Stop the engine as soon as you can do it safely and get it checked before running it again.
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. Cummins rates this a red stop lamp code, so if the red lamp is on, go by the red example.
Keep an eye on it
A one-time crankcase code in freezing weather that cleared once warm.
Schedule a repair
The code keeps returning or oil is seeping from seals. Service the breather soon.
Stop and get help
Oil blowing out of the dipstick tube, heavy blow-by smoke, or a stop lamp. Shut it down. High crankcase pressure can mean serious internal wear.
Common causes
The sensor reading itself is out of range or the condition is real, so look at the system:
- Plugged crankcase breather or filter
- Frozen breather in cold weather
- Disconnected ventilation hose
- High blow-by from worn rings or a failing turbo
What you can check before calling
- Check that the breather hose is connected and not kinked or frozen
- Look for oil being pushed out of the dipstick tube or seals
- Note heavy smoke from the breather tube
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, 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
- 555 SPN 101 FMI 16
Crankcase Pressure: reading above normal (moderately severe) - 1843 SPN 101 FMI 3
Crankcase Pressure Circuit: circuit voltage high / shorted high - 1844 SPN 101 FMI 4
Crankcase Pressure Circuit: circuit voltage low / shorted low - 1942 SPN 101 FMI 2
Crankcase Pressure: erratic or intermittent signal - 1974 SPN 101 FMI 15
Crankcase Pressure: reading above normal (least severe)
Related Crankcase and ventilation codes
- 719 SPN 1264 FMI 3
Crankcase Blowby Pressure Sensor Circuit: circuit voltage high / shorted high - 729 SPN 1264 FMI 4
Crankcase Blowby Pressure Sensor Circuit: circuit voltage low / shorted low - 2699 SPN 520320 FMI 7
Crankcase Depression Valve: not responding / out of adjustment - 3377 SPN 5396 FMI 31
Engine Crankcase Ventilation Hose Disconnected: condition exists - 3733 SPN 862 FMI 3
Crankcase Breather Filter Heater Circuit: circuit voltage high / shorted high - 3734 SPN 862 FMI 4
Crankcase Breather Filter Heater Circuit: circuit voltage low / shorted low
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 556 mean?
Cummins fault code 556 is J1939 SPN 101 FMI 0: Crankcase Pressure - Data valid but above normal operational range - Most Severe Level. In plain terms: crankcase pressure: reading above normal (most severe).
Can I keep driving with Cummins code 556?
No. Cummins assigns this code a red stop lamp. Stop the engine as soon as it's safe and have it checked before running it again. Look at the green, yellow and red examples on this page to judge your situation.
What is the SPN and FMI for Cummins code 556?
SPN 101 identifies the part or system (Engine Crankcase Pressure). FMI 0 describes the type of failure: reading above normal (most severe).
What usually causes Cummins code 556?
The most common causes are: plugged crankcase breather or filter; frozen breather in cold weather; disconnected ventilation hose.
Diesel down in the Midlands?
We work on Cummins-powered pickups, vans and medium-duty trucks across Lexington, Columbia and the Midlands, on site at your yard or roadside.