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Home / Diagnostic Decoder / Powertrain System / Code P0121
System: Powertrain (P-Code) Coverage: SAE Standard (Generic) Fault Family: throttle_position_sensor_circuit

Code P0121: Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance

Diagnostic & Technical Explanation
Code P0121 (Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance) sets when the ECM detects an open, shorted, or out-of-range voltage, or an implausible rate of change, from a throttle body or accelerator pedal position sensor channel. Causes are a worn sensor track, a corroded connector, or chafed wiring between the sensor and the ECM.

Probability-Ranked Repair Procedures (3 Ranked Fixes)

Rank #1

Inspect and clean throttle/pedal position sensor connector

Easy DIY
Parts Estimate: $5.0–$20.0 USD Labor Estimate: 0.4 Shop Hours
  1. 1. Locate the throttle body or accelerator pedal assembly connector
  2. 2. Unplug and inspect for corrosion or bent pins
  3. 3. Clean contacts and reseat firmly
  4. 4. Clear codes and verify smooth voltage sweep
Required Replacement Parts: 🔧 Electrical contact cleaner
Rank #2

Replace throttle body or pedal position sensor assembly

Moderate DIY
Parts Estimate: $60.0–$280.0 USD Labor Estimate: 0.8 Shop Hours
  1. 1. Unplug the connector and remove the mounting fasteners
  2. 2. Install the replacement throttle body or pedal assembly
  3. 3. Reconnect and perform a throttle relearn if required
  4. 4. Clear codes and verify all channels track together
Required Replacement Parts: 🔧 Electronic throttle body assembly · 🔧 Accelerator pedal position sensor assembly
Rank #3

Repair throttle/pedal position sensor wiring

Professional Required
Parts Estimate: $10.0–$60.0 USD Labor Estimate: 1.3 Shop Hours
  1. 1. Back-probe the reference, signal, and ground circuits at the connector
  2. 2. Voltage-drop test each leg back to the ECM
  3. 3. Repair chafed conductors with heat-shrink splices
  4. 4. Confirm all sensor channels agree throughout the pedal/throttle sweep
Required Replacement Parts: 🔧 Automotive wiring repair kit (solder + heat-shrink)

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