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SPN 651 FMI 5

Injector Cylinder #01 — Current below normal or open circuit.
Less current is flowing in an output or sensor circuit than expected, which usually means the circuit is open.

What the SPN covers: Circuit or performance fault for the cylinder 1 fuel injector. More on SPN 651.

What FMI 5 usually points to: Broken wire, unplugged connector, burned-out coil or solenoid, or a backed-out terminal. More on FMI 5.

Severity

HIGH — limit use, diagnose now

Misfire and rough running are likely. Avoid heavy load; a stuck injector can damage the engine.

Likely causes

  1. Wiring or connector fault in this circuit (most common for electrical FMIs)
  2. Injector solenoid circuit open or shorted
  3. Damaged harness under the valve cover
  4. Worn or sticking injector
  5. ECM 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. Run a cylinder cutout / contribution test
  4. Check injector circuit resistance
  5. Inspect harness under the valve cover
  6. Swap injector per OEM procedure if allowed

FAQ

What does SPN 651 FMI 5 mean?

Injector Cylinder #01 — current below normal or open circuit. Less current is flowing in an output or sensor circuit than expected, which usually means the circuit is open.

Is SPN 651 FMI 5 serious?

Misfire and rough running are likely. Avoid heavy load; a stuck injector can damage the engine.

What should I check first for SPN 651 FMI 5?

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; Run a cylinder cutout / contribution test.