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SPN 91 FMI 2 – Accelerator Pedal Learn Error Fault Code (Symptoms, Causes & Fix)

The SPN 91 FMI 2 fault code is a diesel engine fault code indicating an Accelerator Pedal Learn Error. This diagnostic trouble code suggests that the ECM has detected an issue with the accelerator pedal position sensor's ability to learn or calibrate its position correctly. This can affect throttle control and engine performance.

What SPN 91 FMI 2 Means

The SPN 91 FMI 2 fault code represents an error in the accelerator pedal learn process. The ECM monitors the accelerator pedal position sensor to ensure it accurately reports pedal position. When the ECM cannot properly learn or calibrate the pedal position, it triggers this fault code. This can be due to electrical issues or calibration errors.

Common Causes of This Fault Code

  • Faulty accelerator pedal position sensor
  • Improper accelerator pedal calibration
  • Wiring harness issues such as open circuits or short circuits
  • Corroded or loose connectors at the pedal position sensor
  • ECM signal problems

Symptoms Drivers May Notice

When the SPN 91 FMI 2 fault code is active, drivers may experience symptoms such as reduced throttle response, erratic engine performance, or the engine entering a limp mode. These symptoms can affect the drivability of the truck and may lead to further operational issues if not addressed.

How Technicians Diagnose This Fault

Technicians begin diagnosing this fault with a visual inspection of the accelerator pedal and its wiring harness for any signs of damage or corrosion. Next, they use a multimeter to check for proper voltage and ground at the accelerator pedal position sensor connector. A continuity test on the wiring harness between the pedal position sensor and the ECM is also conducted to identify any open or short circuits. Using OEM diagnostic software, technicians verify the accelerator pedal calibration and recalibrate if necessary. Additionally, they check for any related fault codes that might provide further insights into the issue.

Common Misdiagnosis

A common misdiagnosis involves replacing the accelerator pedal assembly without verifying the integrity of the wiring. Technicians might also mistakenly assume a faulty ECM without confirming the functionality of the sensor and wiring. Overlooking the need for recalibration after replacing the pedal or sensor is another frequent error.

Can You Keep Driving?

While it may be possible to continue driving with the SPN 91 FMI 2 fault code active, it is not advisable. The fault can lead to reduced throttle response and potentially cause the engine to enter a derate or protection mode, which could impact the truck's performance and safety. Addressing the issue promptly is recommended to avoid further complications.

Mechanic's Diagnostic Tip

When diagnosing the SPN 91 FMI 2 fault code, always verify the integrity of the wiring and connectors before replacing any components. A thorough electrical test can prevent unnecessary part replacements and ensure the root cause is accurately identified.

Frequently Asked Questions

  • What does SPN 91 FMI 2 indicate? It indicates an error in the accelerator pedal learn process, affecting throttle control.
  • Can a faulty sensor cause SPN 91 FMI 2? Yes, a faulty accelerator pedal position sensor is a common cause.
  • Is recalibration necessary after repairs? Yes, recalibration is often necessary to ensure proper pedal function after repairs.

Other FMI Codes for SPN 91