SPN 1347 FMI 6 — Fuel Pump / Fuel Delivery Control Circuit Current Above Normal
High-current fuel control codes need short isolation before another pump is installed. Repeat fuse failures after pump-only replacement when the harness short remains is the most documented pattern. The FSM stops repeated component failure by requiring short isolation.
Fault Overview
SPN 1347 FMI 6 is a fuel delivery control circuit current above normal or short class fault. Shorted pump motor, harness short to ground or power, water-intruded connectors, and pinched loom are the primary causes. Repeat fuse failures after pump-only replacement when the harness short remains is a documented pattern. Replacing the pump without isolating the short source is the most documented misdiagnosis pattern.
Engine & Platform Coverage
Symptoms
- •Fuel pump circuit shorted
- •Lift pump high current
- •Fuel control short
- •Fuse blows fuel pump circuit
- •Intermittent no-start from pump circuit fault
Possible Causes
- 1.Shorted pump motor — shorted pump motor producing above-normal current
- 2.Harness short to ground or power — harness short producing above-normal current
- 3.Water-intruded connectors — water intrusion producing short circuit
- 4.Pinched loom — loom pinched at frame-rail or battery-box transition 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 — Remove Pump Load: Remove the pump load from the circuit. Disconnect the pump and check if the high-current fault clears. A fault that clears with the pump disconnected confirms a pump fault. A fault that remains with the pump disconnected confirms a harness fault.
- 2Step 2 — Check Harness Shorts: Check the harness for shorts. Inspect frame-rail chafe, battery-box transitions, and pump connector moisture. A harness short to ground or power producing above-normal current requires harness repair. Water intrusion producing a short circuit requires connector service.
- 3Step 3 — Measure Pump Resistance and Current: Measure pump resistance and current draw. Low resistance on the pump circuit supports a shorted pump motor. Current draw above OEM limits supports a failed pump. Compare to OEM specification.
- 4Step 4 — Repair Circuit Before New Pump If Needed: Repair the circuit before installing a new pump if a harness fault is confirmed. A new pump installed into a harness short will fail the new pump and may blow the fuse again. Confirm the harness is clean before any pump replacement.
- 5Step 5 — Replace Pump After Circuit Proof: Replace the pump after circuit proof. Confirm the harness is clean and the short is resolved before pump replacement. Replace relay and fuse as collateral damage if they were damaged by the short.
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Repair Steps
2 steps locked- 1Repair harness if short is confirmed in the harness.
- 2Service connector if water intrusion is confirmed.
- 3Replace pump if pump fault is confirmed after circuit proof.
- 4Replace relay and fuse as collateral damage if damaged.
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 fuel control codes need short isolation before another pump is installed. The AI Diesel Tech FSM stops repeated component failure by requiring short isolation.