Cummins fault code 366

What it means

Cummins' description: Fuel Pump Control Module, Supply Voltage Circuit - data incorrect.

SPN 1077 is Fuel Pump Control Module, Supply Voltage Circuit. FMI 2 means the signal is jumping around, dropping in and out, or doesn't make sense compared to other readings.

Modern Cummins engines build very high fuel pressure in a common rail that feeds the injectors. The ECM controls rail pressure with a fuel pump actuator and monitors it with a rail pressure sensor. A pressure relief valve protects the system.

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

The sensor reading itself is out of range or the condition is real, so look at the system:

• Clogged fuel filters (the most common cause of low rail pressure)
• Air in the fuel from a loose fitting or empty tank
• Weak lift pump or restricted fuel supply
• Worn high-pressure pump
• Injector leaking back too much fuel
• Pressure relief valve opening or leaking

What you can check before calling

• Check when the fuel filters were last changed
• Make sure there's plenty of fuel in the tank
• Look for fuel leaks at the pump, rail and lines
• Notice hard starting, stalling or power loss under load

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: Diagnostic Fault Codes for Cummins Engines. Always confirm with Cummins service information (QuickServe) for your engine serial number.