SPN 91 FMI 2
Accelerator Pedal Position 1 — Data erratic, intermittent, or incorrect.
The signal jumps around, drops in and out, or disagrees with other information the controller has.
What the SPN covers: How far the driver is pressing the throttle pedal, sent as a percentage to the engine computer. More on SPN 91.
What FMI 2 usually points to: Loose or corroded connectors, chafed wiring, a failing sensor, or two redundant sensors that do not agree. More on FMI 2.
Severity
HIGH — limit use, diagnose now
The engine may go to idle-only or limp mode. Do not drive in traffic with an unreliable throttle.
Likely causes
- Worn or failed pedal position sensor
- Corroded pedal connector (common under the cab floor)
- Chafed harness
- Lost 5 V reference shared with other sensors
Checks & fixes (easiest first)
- Watch pedal % on a scan tool while slowly pressing — it should rise smoothly
- Inspect the pedal connector for water and corrosion
- Check the 5 V reference and ground at the pedal
- Check if idle validation switch codes are also present
FAQ
What does SPN 91 FMI 2 mean?
Accelerator Pedal Position 1 — data erratic, intermittent, or incorrect. The signal jumps around, drops in and out, or disagrees with other information the controller has.
Is SPN 91 FMI 2 serious?
The engine may go to idle-only or limp mode. Do not drive in traffic with an unreliable throttle.
What should I check first for SPN 91 FMI 2?
Watch pedal % on a scan tool while slowly pressing — it should rise smoothly; Inspect the pedal connector for water and corrosion; Check the 5 V reference and ground at the pedal.