SPN 655 FMI 6 — Injector Cylinder 5 Circuit Current Above Normal
Overcurrent on injector 5 is isolated by resistance and disconnection.
Fault Overview
FMI 6 indicates overcurrent on cylinder 5 injector circuit, consistent with shorted coil or short-to-ground.
Engine & Platform Coverage
Symptoms
- •Injector 5 short
- •High current cylinder 5
- •SPN 655 FMI 6
Possible Causes
- 1.Shorted coil
- 2.Harness short to ground
- 3.Incorrect injector installed
- 4.Oil contamination path
- 5.Damaged insulation
Wiring & Circuit Notes
Under-cover abrasion and connector contamination checks. Coil shorts and abrasion are primary patterns. Always verify correct part number on replacement.
DVOM Specs & Sensor Tests
Near-zero resistance indicates short. Disconnect isolation to differentiate injector from harness. Compare to sibling injectors.
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 — Resistance Measurement: Measure resistance of injector 5. Near-zero indicates internal short. Compare to sibling cylinders.
- 2Step 2 — Disconnect Isolation: Disconnect injector 5 and recheck for short to ground on the harness side.
- 3Step 3 — Harness Inspection: Inspect under-cover wiring for abrasion and contact with grounded surfaces.
- 4Step 4 — Part Number Verification: Verify correct injector part number and resistance specification.
- 5Step 5 — Single-Circuit Confirmation: Confirm the fault isolates to cylinder 5 and is not a shared circuit issue.
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
Shorted injector or harness repair $200–800+.
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.