SPN 91 FMI 31 is the Detroit fault code for a 2-channel accelerator pedal learned range too large on the DD Series accelerator pedal circuit. This 2-page reference from the DiagTechPro library reproduces the official Detroit troubleshooting steps so a technician can work the fault in the correct order. It is a factory-style diagnostic guide, not a repair shortcut.
Official document details
| Brand | Detroit (Detroit Diesel) |
| Model coverage | DD13, DD15, DD16 – DD Series (EPA 2007–current) |
| System / Group | DD Series (EPA 2007-Current) / DTCs |
| Suspect Parameter Number | 91 |
| Failure Mode Identifier | 31 |
| Description | 2-Channel Accelerator Pedal Learned Range Too Large |
| Coverage / Revision | GHG14 |
| Pages | 2 |
| File size | 0.3 MB |
| Format | |
| Language | English |
Document table of contents
- Fault code identification and description
- Monitoring Accelerator Pedal Position voltage
- Full-sweep pedal travel test
- Harness wiggle and vibration test
- Clearing codes and verifying the repair
SPN 91 FMI 31 diagnostic overview
SPN 91 FMI 31 is logged when the two-channel accelerator pedal reports a learned range that is too large. The procedure has the technician monitor Accelerator Pedal Position voltage on the diagnostic tool, cycle the pedal through a full sweep of travel, then gently wiggle the pedal and harness connector to simulate road vibration before deciding to replace the pedal. Where the fault will not clear, the guide directs the technician to obtain a log file and contact the Detroit™ Customer Support Center at 800-445-1980. Each step is written as a yes or no decision, so the result of one measurement points directly to the next check or to the final repair action.
Applicable truck models and engines
It applies to Detroit DD13, DD15 and DD16 engines in the DD Series (EPA 2007 to current) family, and the library also carries the matching guide for the Series 60 (DDEC VI) platform. For factory support tools and warranty information, see Demand Detroit official resources.
Who needs this SPN 91 FMI 31 manual
This document is written for Detroit truck technicians and workshop owners diagnosing an accelerator pedal (AP) complaint on DD Series engines, so they can confirm a faulty pedal instead of replacing parts by guesswork.
The full PDF is available in the DiagTechPro manuals library; a free account is required to download it, view every page, and print the decision steps for use at the workshop bench.
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