SPN 663 FMI 5 — Injector Cylinder 13 Circuit Open
Cylinder 13 open is wiring until the injector itself proves open. Cylinder-local circuit gates prevent multi-injector shotgun repairs. The ECM monitors injector driver current during commanded injection and sets FMI 5 when the expected current rise is missing.
Fault Overview
SPN 663 FMI 5 is a cylinder 13 injector circuit open or low-current class fault. The ECM monitors injector driver current during commanded injection and sets FMI 5 when expected current rise is absent. Unseated connector, open harness branch, failed injector winding or piezo path, pass-through pin backout, and oil or corrosion intrusion are the primary causes. Service-induced opens after injector R&R and vibration fatigue at flex loops are documented patterns. Replacing the injector before proving the circuit is the most documented misdiagnosis pattern.
Engine & Platform Coverage
Symptoms
- •Injector 13 open circuit
- •Cylinder 13 misfire
- •Injector wiring open
- •No contribution cylinder 13
- •Active misfire increasing soot
Possible Causes
- 1.Unseated connector — unseated cylinder 13 connector producing open circuit
- 2.Open harness branch — open harness branch producing no current path to injector
- 3.Failed injector winding or piezo path — failed injector internal path producing open circuit
- 4.Pass-through pin backout — pass-through pin backed out producing open circuit
- 5.Oil or corrosion intrusion — oil or corrosion intrusion producing open circuit
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
4 steps locked behind Technician Mode- 1Step 1 — Visual Connector Seat: Inspect the cylinder 13 connector lock, under-cover pass-through pins, and chafe points near valve-cover edges and brackets. Service-induced opens after injector R&R are a documented pattern — always inspect the connector after any recent injector service. Confirm the connector is fully seated and locked.
- 2Step 2 — Resistance Test: Measure injector resistance against OEM specification. OL or high resistance versus OEM injector specification supports an open injector winding. Compare to adjacent cylinder injectors as a reference, but use OEM specification as the standard.
- 3Step 3 — Continuity to Controller: Check continuity from the driver connector to the injector. A continuity loss from the driver connector to the injector confirms a harness or connector fault. Confirm insulation integrity before re-commanding injection.
- 4Step 4 — Isolate Harness vs Injector: Isolate the harness from the injector. A resistance fault that clears with the injector disconnected confirms a harness fault. A resistance fault that remains with the injector disconnected confirms an injector internal fault.
- 5Step 5 — Replace Injector Only After Internal Open Is Proven: Replace the injector only after an internal open is proven. Confirm the harness and connector are clean before injector replacement. An injector replaced into a harness open will not resolve the fault.
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Repair Steps
1 steps locked- 1Repair harness or connector if open circuit is confirmed in the harness.
- 2Replace injector with coding or trim where required if internal open is confirmed ($300–$900+).
- 3Inspect and repair pass-through pins if backout is confirmed.
Unlock full diagnostic steps, DVOM tests, and repair procedures.
Full Diagnostic Access
Verification steps, preventative measures, severity guidance, and legacy comparison are available in Technician Mode.
Start Diagnosing This Fault Now
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Summary
Cylinder 13 open is wiring until the injector itself proves open. The AI Diesel Tech FSM enforces cylinder-local circuit gates to prevent multi-injector shotgun repairs.