AI Diesel Tech
P0121OBD-IISENSOR

Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance

Common Symptoms

  • Check Engine Light illuminated
  • Poor acceleration or hesitation during throttle application
  • Engine may idle rough or stall
  • Transmission may exhibit harsh or delayed shifts
  • Reduced engine power or limp mode activation
  • Unstable idle speed

Most Likely Root Causes

  • Faulty throttle position sensor
  • Dirty or carbon-fouled throttle body
  • Damaged or corroded wiring harness to throttle position sensor
  • Poor electrical connection at throttle position sensor connector
  • Failed throttle body assembly

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Component Location

The throttle position sensor is integrated into the throttle body assembly, typically located between the air intake and intake manifold.

Manufacturer Notes

Some manufacturers require throttle body relearn or idle adaptation procedures after cleaning or replacement to prevent this code.

Also diagnosing J1939 SPN/FMI codes?

Heavy-duty trucks often throw both OBD-II and J1939 faults simultaneously. AI Diesel Tech handles both protocols in a single guided session.

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