SPN 97 FMI 5 — Water-in-Fuel Sensor Circuit Open / Current Below Normal
Open circuit on the WIF sensor is confirmed by resistance and continuity before replacement.
Fault Overview
FMI 5 indicates an open circuit or current below expected on the WIF sensor. The ECM cannot complete the detection circuit.
Engine & Platform Coverage
Symptoms
- •WIF sensor open circuit code
- •Water-in-fuel sensor inoperative
- •No WIF detection capability
- •Loss of water warning
Possible Causes
- 1.Open sensor element
- 2.Broken signal or ground wire
- 3.Unplugged connector
- 4.High-resistance corrosion at pins
- 5.Failed ECM sense circuit (rare)
Wiring & Circuit Notes
Corroded pins and broken wires at the filter housing flex point are frequent open-circuit causes. Check connector engagement, pin tension, and corrosion. Continuity test both signal and ground circuits.
DVOM Specs & Sensor Tests
Sensor continuity or resistance within specification. Open reads infinite. Continuity from ECM to sensor pins. Ground circuit voltage drop under any load.
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 — Inspect Connector Engagement: Check connector for full engagement and corrosion. Corroded pins and broken wires at the filter housing flex point are frequent open-circuit causes.
- 2Step 2 — Measure Sensor Resistance: Measure sensor resistance. Open reads infinite. Compare to OEM specification for a dry bowl.
- 3Step 3 — Continuity Test Signal Wire: Continuity test the signal wire from the sensor connector to the ECM pin.
- 4Step 4 — Continuity Test Ground Wire: Continuity test the ground circuit. Check for high resistance at pins under any load.
- 5Step 5 — Check for High Resistance: Measure resistance at each pin contact. High resistance from corrosion can cause open-circuit detection even with physical continuity.
- 6Step 6 — Replace or Repair as Isolated: Replace open sensor, repair open wire, or service connector as the test results indicate.
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
Replace open sensor $40–120; repair open wire $50–100; service connector $30–60. Total typical $45–180.
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.