Cummins fault code 546

What it means

Cummins' description: Fuel Delivery Pressure Sensor Circuit - Voltage above normal, or shorted to high source.

SPN 94 is Engine Fuel Delivery Pressure. 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 low-pressure side supplies fuel from the tank to the high-pressure pump. It includes the lift pump, fuel filters, water separator, fuel temperature sensor and water-in-fuel sensor.

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:

• Water-in-fuel sensor or fuel temperature sensor failed
• Lift pump circuit or relay fault
• Connector damage at the filter head

If the circuit checks out, the reading may be real. Other possibilities: water in the fuel or a full water separator bowl; clogged fuel filter; weak or failed lift pump.

What you can check before calling

• Drain the water separator and see if water comes out
• Check when the fuel filters were last changed
• Make sure the tank isn't low, especially on a slope
• In cold weather, think about fuel gelling

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, QSB 4.5, QSF 3.8. 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.