SPN 91 FMI 0 — Accelerator Pedal Position Above Normal
APP above-normal is rest-position and circuit integrity diagnosis with safety priority. Safety limp strategies triggered by one channel reading high at rest — when the cause was an open ground or failed track — is the most documented pattern.
Fault Overview
SPN 91 FMI 0 indicates the accelerator pedal position is reported above the calibrated maximum or in an implausible high range. Failed pedal track reading high, open ground producing a high-signal condition, short to voltage on the signal wire, connector contamination, and mechanical pedal binding are the primary causes. Electrical high is more common than mechanical binding.
Engine & Platform Coverage
Possible Causes
- 1.Failed pedal track reading high at rest from internal failure
- 2.Open ground at pedal connector producing high-signal condition
- 3.Short to voltage on APP signal wire
- 4.Connector contamination biasing signal high
- 5.Mechanical pedal binding — less common than electrical high
Wiring & Circuit Notes
Verify the pedal mechanically returns to rest before any electrical diagnosis. High at rest with good mechanical return points to electrical or failed track. Ground integrity at the pedal connector is a common cause of high-signal conditions.
DVOM Specs & Sensor Tests
Verify pedal mechanically returns to rest position. Graph both channels at rest and through full sweep. Pedal released should be at idle range — high at rest with good mechanical return is electrical or failed track. Check ground and signal integrity at pedal connector. Replace pedal assembly after circuit is proven.
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
6 steps locked behind Technician Mode- 1Verify pedal mechanically returns to rest position
- 2Graph both APP channels at rest and through full sweep
- 3Check ground integrity at pedal connector
- 4Check signal wire for short to voltage
- 5High at rest with good mechanical return — diagnose electrical or failed track
- 6Replace pedal assembly after circuit is proven
- 7Verify rest-position values are in idle range before release
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Repair Steps
5 steps locked- 1Verify pedal mechanically returns to rest position
- 2Graph both APP channels at rest and through full sweep
- 3Check ground integrity at pedal connector
- 4Check signal wire for short to voltage
- 5High at rest with good mechanical return — diagnose electrical or failed track
- 6Replace pedal assembly after circuit is proven
- 7Verify rest-position values are in idle range before release
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.
Related Resources
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Summary
SPN 91 FMI 0 is rest-position and circuit integrity diagnosis with safety priority. Mechanical return and electrical proof are required before control-module conclusions.