SPN 97 FMI 3 — Water-in-Fuel Sensor Circuit Voltage Above Normal
High voltage on the WIF sensor circuit is an open or short-to-power until wiring and sensor resistance are proven.
Fault Overview
FMI 3 indicates voltage above the high threshold on the WIF sensor circuit. The ECM sees an open circuit or short-to-power condition that prevents valid water detection.
Engine & Platform Coverage
Symptoms
- •WIF sensor high voltage code
- •Water-in-fuel circuit open
- •No water detection capability
- •WIF lamp behavior abnormal
Possible Causes
- 1.Open sensor element
- 2.Open signal wire
- 3.Short to battery voltage
- 4.Corroded or unplugged connector
- 5.Failed ECM pull-up circuit (rare)
Wiring & Circuit Notes
Corrosion at the sensor connector after repeated drain cycles or road salt exposure is the dominant cause of high-voltage codes. Inspect and clean before any electrical measurement.
DVOM Specs & Sensor Tests
Sensor resistance or voltage with dry bowl per OEM chart. Open circuit typically produces high voltage on a pull-up design. Measure voltage at the sensor connector and at the ECM with sensor connected and disconnected.
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
6 steps locked behind Technician Mode- 1Step 1 — Inspect and Clean Connector: Inspect and clean the connector at the filter housing. Check for corrosion and pin tension.
- 2Step 2 — Measure Voltage with Sensor Connected: Measure voltage on the signal circuit with sensor connected. Note the reading.
- 3Step 3 — Measure Voltage with Sensor Disconnected: Disconnect the sensor and remeasure voltage. If voltage drops significantly, the sensor is pulling the circuit high (open sensor element).
- 4Step 4 — Check Sensor Resistance: Measure sensor resistance or continuity and compare to OEM dry-bowl specification.
- 5Step 5 — Continuity Test Signal Wire: Perform continuity test on the signal wire from the sensor connector to the ECM.
- 6Step 6 — Check for Short to Power: Check for short to battery voltage on the signal wire along the harness route.
- 7Step 7 — Substitute Sensor: Substitute sensor only after wiring is proven good.
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
Repair open or shorted wire $50–120; replace corroded connector $40–80; replace failed sensor $40–120. Total typical $50–220.
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.