SPN 91 — Accelerator Pedal Position 1
System: Throttle
How far the driver is pressing the throttle pedal, sent as a percentage to the engine computer.
Can I keep running it?
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
Common FMIs with SPN 91
- SPN 91 FMI 2Data erratic, intermittent, or incorrect
- SPN 91 FMI 3Voltage above normal or shorted high
- SPN 91 FMI 4Voltage below normal or shorted low
- SPN 91 FMI 19Received network data in error
Related codes
- SPN 190Engine Speed
FAQ
What does SPN 91 mean?
SPN 91 is Accelerator Pedal Position 1. How far the driver is pressing the throttle pedal, sent as a percentage to the engine computer.
Can I keep running with SPN 91?
The engine may go to idle-only or limp mode. Do not drive in traffic with an unreliable throttle.
What causes SPN 91?
Worn or failed pedal position sensor; Corroded pedal connector (common under the cab floor); Chafed harness; Lost 5 V reference shared with other sensors.