Cummins fault code 1548

What it means

Cummins' description: Injector Solenoid Driver Cylinder 7 Circuit - Current below normal or open circuit.

SPN 657 is Engine Injector Cylinder #7. FMI 5 means the ECM is driving the circuit but almost no current flows, which usually means an open circuit: a broken wire, unplugged connector, or failed coil.

Each cylinder has an electronically controlled fuel injector. The ECM watches each injector's circuit and how each cylinder is contributing, and flags misfires or fueling errors.

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

• Injector wiring or connector fault (often under the valve cover)
• Shorted or open injector solenoid
• ECM injector driver problem

If the circuit checks out, the reading may be real. Other possibilities: worn or sticking injector; low compression in that cylinder; fuel supply or rail pressure problem.

What you can check before calling

• Note rough idle, shaking, white or black smoke, or a knocking sound
• Check whether the misfire is constant or only cold
• Check recent fuel filter service and fuel quality

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.