SPN 665 FMI 5 — Injector Cylinder 15 Circuit Open
Open on cylinder 15 follows the standard circuit-to-component sequence. Incomplete connector latch after injector service is the most documented pattern. The FSM keeps diagnosis cylinder-local and evidence-based.
Fault Overview
SPN 665 FMI 5 is a cylinder 15 injector circuit open or low-current class fault. Open connector, broken conductor, failed injector, damaged pass-through, and corrosion are the primary causes. Incomplete connector latch after injector service is a documented pattern. Replacing the cylinder 15 injector before proving the circuit path is the most documented misdiagnosis pattern.
Engine & Platform Coverage
Symptoms
- •Injector 15 open
- •Cylinder 15 misfire
- •Injector wire broken cylinder 15
- •No contribution cylinder 15
- •Rough running under load
Possible Causes
- 1.Open connector — open connector at cylinder 15 producing open circuit
- 2.Broken conductor — broken conductor in cylinder 15 harness branch
- 3.Failed injector — failed injector internal path producing open circuit
- 4.Damaged pass-through — damaged pass-through terminal producing open circuit
- 5.Corrosion — corrosion producing open circuit
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
3 steps locked behind Technician Mode- 1Step 1 — Visual Seat and Lock: Inspect the cylinder 15 connector seat and lock. Verify lock tabs after any valve-cover work. Incomplete connector latch after injector service is 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 specification supports an open injector winding. Verify the cylinder 15 branch plus shared under-cover connectors.
- 3Step 3 — Continuity Check: Check continuity from the driver to the injector. A continuity failure to the ECM or driver confirms a harness or connector fault. Verify no short before retest.
- 4Step 4 — Component Replace Only After Circuit Proof: Replace the injector only after circuit proof. Confirm the harness and connector are clean before injector replacement. A new injector installed 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 connector or harness if open circuit is confirmed in the harness.
- 2Replace injector if internal open is confirmed after circuit proof.
- 3Repair pass-through terminal if backout or damage 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
AI Diesel Tech walks you through every evidence gate in the correct order. Choose the plan that fits your shop.
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Summary
Open on cylinder 15 follows the standard circuit-to-component sequence. The AI Diesel Tech FSM keeps diagnosis cylinder-local and evidence-based.