SPN 107 FMI 2 — Air Filter Restriction Data Erratic
Erratic restriction data is sensing integrity first. Repeat filter replacements for an intermittent restriction sensor is the most documented pattern on this fault class.
Fault Overview
SPN 107 FMI 2 indicates the air filter restriction data is unstable or implausible. Failing restriction sensor, intermittent harness, loose sense hose, moisture in sense lines, and actual intermittent debris packing are the primary causes — with sensing issues being far more common than actual intermittent loading. Sense-hose security and sensor circuit proof are required before any filter over-service.
Engine & Platform Coverage
Symptoms
- •Restriction reading jumping erratically on scan tool
- •Intermittent restriction code with no consistent filter loading
- •Restriction sensor reading unstable during steady road load
- •Repeat filter replacements without resolving the erratic reading
- •Sense hose loose at the filter housing
Possible Causes
- 1.Failing restriction sensor with intermittent output
- 2.Intermittent harness fault at the restriction sensor connector
- 3.Loose sense hose at the filter housing
- 4.Moisture in the sense line producing erratic readings
- 5.Actual intermittent debris packing — less common than sensing issues
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 — Inspect Hose and Connector: Inspect the sense hose for looseness, kinks, or moisture. Inspect the restriction sensor connector for fretting or corrosion. A loose sense hose or corroded connector is the most common cause of erratic restriction data.
- 2Step 2 — Wiggle Test: Perform a wiggle test on the restriction sensor connector and harness while monitoring the restriction reading on the scan tool. An abrupt change in reading during the wiggle test confirms an intermittent harness or connector fault.
- 3Step 3 — Circuit Checks: Perform circuit checks on the restriction sensor — reference voltage stability, signal voltage, and ground integrity. Unstable reference or ground can produce erratic restriction data.
- 4Step 4 — Graph Restriction During Steady Road Load: Graph the restriction reading during steady road load. Abrupt electrical swings differ from gradual filter loading. Electrical dropouts are instantaneous; real filter loading is gradual.
- 5Step 5 — Sensor Replacement After Proof: Replace the restriction sensor only after the sense hose, connector, and circuit are confirmed intact and the sensor itself is proven to be the source of the erratic data.
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Repair Steps
3 steps locked- 1Secure loose sense hose at the filter housing.
- 2Repair corroded or fretting restriction sensor connector.
- 3Repair intermittent harness fault at the restriction sensor.
- 4Drain moisture from sense line.
- 5Replace restriction sensor after circuit proof confirms sensor instability.
Unlock full diagnostic steps, DVOM tests, and repair procedures.
Full Diagnostic Access
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Summary
SPN 107 FMI 2 is a sensing integrity fault. Secure the sense hose, prove the circuit, and replace the sensor after proof before evaluating true filter loading.