SPN 2623 FMI 3 — Accelerator Pedal Position Sensor 2 Circuit Voltage Above Normal
APP2 high-voltage codes are channel-2 open-circuit diagnostics. Entire pedal assemblies condemned as 'bad' without identifying which channel circuit failed is the most documented waste on this fault.
Fault Overview
SPN 2623 FMI 3 indicates APP channel 2 circuit voltage is above the valid maximum — an open circuit or high-signal class fault on dual-sensor pedal systems. Open APP2 signal wire, failed second track, unplugged dual-track connector pin, and reference issues on channel 2 supply where split are the primary causes.
Engine & Platform Coverage
Possible Causes
- 1.Open APP2 signal wire from damage at firewall or floor connector
- 2.Failed second pedal track with internal open element
- 3.Unplugged dual-track connector pin for channel 2
- 4.Reference issues on channel 2 supply where split from channel 1
- 5.Terminal tension loss at channel 2 cavity in pedal connector
Wiring & Circuit Notes
Compare APP1 versus APP2 simultaneously. Channel 2 open or high with channel 1 healthy isolates the APP2 path. Inspect pedal connector cavities specific to channel 2 and check terminal tension.
DVOM Specs & Sensor Tests
Graph APP1 and APP2 simultaneously through full sweep. Channel 2 open or high with channel 1 responding normally isolates the APP2 circuit. Check channel 2 open-circuit continuity from pedal connector to ECM. Verify supply and ground for channel 2. Replace pedal assembly after channel 2 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- 1Graph APP1 and APP2 simultaneously through full pedal sweep
- 2Confirm channel 2 open or high with channel 1 responding normally
- 3Check channel 2 open-circuit continuity from pedal connector to ECM
- 4Verify supply and ground for channel 2
- 5Inspect pedal connector cavities for channel 2 terminal tension
- 6Replace pedal assembly after channel 2 circuit is proven
- 7Verify both channels correlate after repair
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Repair Steps
5 steps locked- 1Graph APP1 and APP2 simultaneously through full pedal sweep
- 2Confirm channel 2 open or high with channel 1 responding normally
- 3Check channel 2 open-circuit continuity from pedal connector to ECM
- 4Verify supply and ground for channel 2
- 5Inspect pedal connector cavities for channel 2 terminal tension
- 6Replace pedal assembly after channel 2 circuit is proven
- 7Verify both channels correlate after repair
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
Related Systems
Related Fault Codes
Related Sensor Locations
Common Symptoms
Related Articles
AI Diesel Tech — The Technician's Diagnostic Engine
AI Diesel Tech diagnostic logic is built by an ASE Certified Diesel Technician and engineered for professional shop use. Trusted by technicians nationwide — used in shops, fleets, and training programs.
Summary
SPN 2623 FMI 3 is a channel-2 open-circuit diagnosis. Channel-specific isolation is required before pedal condemnation.