D21-6005 | Genuine Paccar® Throttle Pedal Assembly

• Peterbilt 379 with Cummins engine
• Peterbilt 335 with Cummins engine
• Peterbilt 386 with Cummins ISX engine
• Other Peterbilt heavy-duty trucks

• Controls acceleration: Pressing the pedal tells the engine to produce more power, making the vehicle speed up.
• Regulates engine air intake: In most modern vehicles, the pedal sends an electronic signal to the engine control module (ECM), which adjusts the throttle valve to let in more or less air.
• Improves fuel efficiency: The ECM can precisely control the throttle based on pedal input, engine speed, load, and other factors to optimize fuel consumption.
• Enhances safety: Modern throttle pedal assemblies often contain two or more position sensors that constantly compare readings. If the signals don't match, the ECM can detect a fault and limit engine power (called "limp mode") to help reduce the risk of unintended acceleration.
• Supports vehicle features: Because the pedal is electronic in most vehicles, it can work with systems such as:
  • Cruise control
  • Traction control
  • Stability control
  • Adaptive cruise control
  • Automatic start-stop systems

1. Poor or delayed acceleration
   • You press the accelerator, but the vehicle responds slowly or not at all.
2. Reduced engine power (Limp Mode)
   • The vehicle limits engine power to protect itself.
   • You may see a "Reduced Engine Power" message on the dashboard.
3. Inconsistent acceleration
   • The vehicle accelerates unevenly or surges even though you're holding the pedal steady.
4. No response from the accelerator
   • Pressing the pedal has little or no effect on engine speed.
5. Check Engine Light
   • The ECM detects an abnormal signal from the accelerator pedal position sensor and stores a fault code.
6. Engine hesitation
   • The engine hesitates or stumbles when you try to accelerate, especially from a stop.
7. Cruise control stops working
   • Cruise control may be disabled because the vehicle cannot reliably determine pedal position.
8. Difficulty maintaining speed
   • The vehicle may unexpectedly lose power or have trouble keeping a constant speed.

Common diagnostic trouble codes (DTCs)

A scan tool may show codes such as:

• P2122 – Accelerator Pedal Position Sensor "D" Circuit Low
• P2123 – Accelerator Pedal Position Sensor "D" Circuit High
• P2127 – Accelerator Pedal Position Sensor "E" Circuit Low
• P2128 – Accelerator Pedal Position Sensor "E" Circuit High
• P2138 – Accelerator Pedal Position Sensor correlation fault