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SPN 654 FMI 6

Injector Cylinder #04 — Current above normal or grounded circuit.
More current is flowing than expected, which usually means a short or a failing load.

What the SPN covers: Circuit or performance fault for the cylinder 4 fuel injector. More on SPN 654.

What FMI 6 usually points to: Shorted solenoid or actuator coil, a wire chafed to ground, or water in a connector. More on FMI 6.

Severity

HIGH — limit use, diagnose now

Misfire and rough running are likely. Avoid heavy load; a stuck or leaking injector can wash down the cylinder or dilute the oil.

Likely causes

  1. Wiring or connector fault in this circuit (most common for electrical FMIs)
  2. Injector solenoid circuit open or shorted
  3. Chafed harness or loose terminal nut under the valve cover
  4. Worn, sticking or leaking injector
  5. Connector (feed) tube or seal problem
  6. ECM injector driver fault

Checks & fixes (easiest first)

  1. Inspect the connector and harness for this circuit: corrosion, water, chafing, backed-out pins
  2. Check the reference voltage, ground and signal at the component per OEM pin-out
  3. Check the FMI — open/short FMIs point to wiring and the coil first
  4. Read balance rates and run a cylinder cutout / contribution test
  5. Measure injector return flow, isolating cylinder 4 per the OEM procedure
  6. Inspect the harness under the valve cover and check oil level for fuel dilution

Troubleshooting guides

FAQ

What does SPN 654 FMI 6 mean?

Injector Cylinder #04 — current above normal or grounded circuit. More current is flowing than expected, which usually means a short or a failing load.

Is SPN 654 FMI 6 serious?

Misfire and rough running are likely. Avoid heavy load; a stuck or leaking injector can wash down the cylinder or dilute the oil.

What should I check first for SPN 654 FMI 6?

Inspect the connector and harness for this circuit: corrosion, water, chafing, backed-out pins; Check the reference voltage, ground and signal at the component per OEM pin-out; Check the FMI — open/short FMIs point to wiring and the coil first.