SPN 664 FMI 6 — Injector Cylinder 14 Circuit Current Above Normal
High-current injector faults are short diagnostics first. The FSM protects ECM drivers and avoids replacing good injectors on harness shorts. Minimize run time until the short is isolated.
Fault Overview
SPN 664 FMI 6 is a cylinder 14 injector circuit current above normal or short class fault. Internal injector short, harness short to power or ground, oil-bridged terminals, and pinched loom after service are the primary causes. Oil intrusion creating intermittent high-current faults and harness damage after in-frame service are documented patterns. Replacing the injector before isolating the short source is the most documented misdiagnosis pattern — a new injector installed into a harness short will fail the new injector and may damage the ECM driver.
Engine & Platform Coverage
Symptoms
- •Injector 14 shorted
- •Cylinder 14 high current
- •Injector short circuit
- •Misfire shorted injector
- •Active misfire with high current fault
Possible Causes
- 1.Internal injector short — internal injector short producing above-normal current
- 2.Harness short to power or ground — harness short producing above-normal current
- 3.Oil-bridged terminals — oil bridging connector terminals producing short circuit
- 4.Pinched loom after service — loom pinched after service producing short 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 — Disconnect Injector: Disconnect the cylinder 14 injector. Avoid repeated actuation into a shorted driver. A short that clears with the injector disconnected confirms an internal injector short. A short that remains with the injector disconnected confirms a harness fault.
- 2Step 2 — Isolate Harness vs Component: Isolate the harness from the component. Inspect insulation rub-through on bracket edges, valve-cover corner damage, and oil-filled connectors. Oil intrusion creating intermittent high-current faults is a documented pattern — inspect the connector for oil intrusion.
- 3Step 3 — Resistance and Short Tests: Perform resistance and short tests. Resistance below OEM minimum supports an internal short. Check short-to-power and short-to-ground with the injector disconnected. A short that remains with the injector disconnected confirms a harness fault.
- 4Step 4 — Repair Circuit Before Installing New Injector If Harness Is at Fault: Repair the circuit before installing a new injector if the harness is at fault. A new injector installed into a harness short will fail the new injector and may damage the ECM driver. Confirm the harness is clean before any injector replacement.
- 5Step 5 — Replace Injector With Coding After Circuit Proof: Replace the injector with coding or trim where required after circuit proof. Confirm the harness is clean and the short is resolved before injector replacement.
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Repair Steps
1 steps locked- 1Repair harness if short is confirmed in the harness.
- 2Replace injector with coding or trim where required if internal short is confirmed.
- 3Inspect and repair oil-intruded connector if oil bridging 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
High-current injector faults are short diagnostics first. The AI Diesel Tech FSM protects ECM drivers and avoids replacing good injectors on harness shorts.