SPN 655 FMI 5 — Injector Cylinder 5 Circuit Open
Open on injector 5 is proven by resistance and continuity before injector replacement.
Fault Overview
SPN 655 FMI 5 indicates open circuit or low current on injector cylinder 5 when commanded. Detection occurs during actuation when driver current does not rise as expected.
Engine & Platform Coverage
Symptoms
- •Injector cylinder 5 open
- •Cylinder 5 misfire
- •SPN 655 FMI 5
- •No contribution cylinder 5
Possible Causes
- 1.Open coil
- 2.Broken wire
- 3.Poor connector
- 4.Oil intrusion
- 5.Open driver
Wiring & Circuit Notes
Cylinder 5 connector and under-cover harness inspection for oil, pins, and chafing. Oil-soaked connectors and harness chafing dominate open-circuit failures across platforms.
DVOM Specs & Sensor Tests
Resistance match to other cylinders. Continuity ECM to injector. Current during command. Open reads infinite resistance.
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
5 steps locked behind Technician Mode- 1Step 1 — Resistance Comparison: Measure resistance of injector 5 and compare to all other cylinders. Open reads infinite.
- 2Step 2 — Continuity Check ECM to Injector: Continuity test from ECM driver pins to the injector connector. Identify the open segment.
- 3Step 3 — Connector Inspection: Inspect cylinder 5 connector and under-cover harness for oil, pin tension, and chafing.
- 4Step 4 — Current Monitoring if Available: Command injector and monitor current if scan tool capability is available.
- 5Step 5 — Isolation Swap if Practical: Swap connector with an adjacent cylinder if safe and accessible to isolate harness vs injector.
- 6Step 6 — Driver Evaluation Last: Evaluate ECM driver only after external circuit is proven.
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Full Diagnostic Access
Verification steps, preventative measures, severity guidance, and legacy comparison are available in Technician Mode.
Typical Repair Costs
Harness or connector repair $100–300; injector if coil open $300–700. Total $150–700.
Start Diagnosing This Fault Now
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Summary
Use the AI Diesel Tech diagnostic engine to run this code through a structured, evidence-gated sequence and get a confirmed root cause before any parts are replaced.