SPN 91 FMI 31 – 2-Channel Accelerator Pedal Learned Range to Large Fault Code (Symptoms, Causes & Fix)

Mar 15, 2026

The SPN 91 FMI 31 fault code is a diesel engine diagnostic trouble code indicating that the 2-channel accelerator pedal learned range is too large. This code suggests an issue with the accelerator pedal position sensor, where the Engine Control Module (ECM) detects a discrepancy in the expected range of pedal position signals.

What SPN 91 FMI 31 Means

When the SPN 91 FMI 31 fault code is active, it means the ECM has identified that the learned range of the accelerator pedal position sensor is larger than expected. This typically involves the sensor's signal not aligning with the pre-programmed parameters, which can affect throttle response and engine performance.

Common Causes of This Fault Code

Faulty accelerator pedal position sensor
Incorrect pedal calibration
Wiring harness issues such as open circuits or short circuits
Corroded or loose connectors
ECM signal processing errors

Symptoms Drivers May Notice

Drivers may experience symptoms such as erratic throttle response, reduced engine power, or unexpected acceleration behavior. In some cases, the engine may enter a derate mode to protect itself from potential damage.

How Technicians Diagnose This Fault

Diagnosing the SPN 91 FMI 31 fault code involves a systematic approach. Start with a visual inspection of the accelerator pedal for any physical damage or obstruction. Check the wiring harness and connectors for signs of damage, corrosion, or loose connections. Use a multimeter to test the voltage and continuity of the accelerator pedal position sensor circuits. Perform a recalibration of the accelerator pedal using the appropriate diagnostic tool. Verify the sensor output using a scan tool to ensure it is within the expected range.

Common Misdiagnosis

Technicians often misdiagnose this fault by replacing the accelerator pedal assembly without verifying sensor calibration. Another common mistake is overlooking wiring harness issues and focusing solely on the sensor. Additionally, assuming a mechanical issue with the pedal when it is an electrical fault can lead to unnecessary repairs.

Can You Keep Driving?

While it may be possible to continue driving with the SPN 91 FMI 31 fault code active, it is not advisable. The fault can lead to unpredictable throttle response and potential engine derate, which could compromise safety and performance. It is recommended to address the issue promptly to avoid further complications.

Mechanic's Diagnostic Tip

When troubleshooting the SPN 91 FMI 31 fault code, always verify the integrity of the wiring harness and connectors before replacing any components. Many issues stem from poor electrical connections rather than sensor failures.

Frequently Asked Questions

Q1: What tools are needed to diagnose SPN 91 FMI 31?
A1: A multimeter and a diagnostic scan tool are essential for testing voltage, continuity, and sensor output.

Q2: Can a faulty ECM cause SPN 91 FMI 31?
A2: While rare, ECM signal processing errors can contribute to this fault code. However, it's crucial to rule out sensor and wiring issues first.

Q3: How often should the accelerator pedal be recalibrated?
A3: Recalibration is typically only necessary after repairs or replacements involving the accelerator pedal or ECM.