Cummins fault code 4286

What it means

Cummins' description: Closed Crankcase Ventilation System Pressure Sensor - Voltage Above Normal, or Shorted to High Source.

SPN 520595 is Closed Crankcase Ventilation System Pressure Sensor. FMI 3 means the voltage on the circuit is higher than possible for a good sensor, usually an open signal wire, a short to a power wire, or a failed sensor.

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

An amber (yellow) warning lamp means the engine can usually keep running, but the fault should be repaired soon, ideally the same day.

Common causes

FMI 3 is an electrical or signal fault, so start with the circuit:

• Crankcase pressure sensor failed or wiring fault
• Breather heater circuit fault

If the circuit checks out, the reading may be real. Other possibilities: plugged crankcase breather or filter; frozen breather in cold weather; disconnected ventilation hose.

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

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.