01 P0031 H02S heater control circuit low (Bank 1 sensor 1) • 02 How Airless Tires Can Change the Future of Driving • 03 Why A Car That Randomly Jerks Forward Might Be Warning Of T… • 04 Why are not all tires on a car the same width? • 05 Alternator Versus Battery Which One Actually Keeps Your Car… • 06 What Happens If You Drop The Anchor At Full Speed? • 07 Unveiling the Secrets of Trailers' Mysterious Extra Wheel O… • 08 This Is Why Mixing Fuel Grades Or Pumping The Wrong Fuel De… • 09 The 9 Silent Signs of a Failing Oxygen Sensor • 10 These Simple Car Maintenance Hacks Have Never Been This Easy •

DTC codes / P21xx · Fuel and air metering / P2129

P2129Throttle/Pedal Position Sensor/Switch 'E' Circuit Intermittent

P2129 means the engine computer has detected an intermittent electrical fault in the Throttle/Pedal Position Sensor/Switch 'E' circuit, which is a secondary sensor track used to cross-check the main pedal or throttle position signal. The computer monitors this circuit for brief dropouts, spikes, or erratic voltage changes and sets the code when the signal becomes unreliable for a fraction of a second.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering

Symptoms you may notice

  • The check engine light is on, often with no other noticeable symptoms.
  • The accelerator pedal may feel unresponsive or have a dead spot during light throttle application.
  • The engine may enter limp mode, limiting speed and RPM without warning.
  • Intermittent hesitation or surging while cruising at a steady speed.
  • The transmission may shift harshly or refuse to downshift because it relies on throttle position data.

Common causes, most likely first

  1. Worn or contaminated electrical contacts inside the accelerator pedal position sensor assembly.
  2. A chafed or broken wire in the sensor 'E' circuit harness, often near the pedal or firewall.
  3. Corrosion or water intrusion at the sensor connector, causing intermittent opens.
  4. A failing throttle body actuator or position sensor on electronic throttle vehicles, where sensor 'E' is part of the throttle body.
  5. Loose or damaged engine computer pins for the sensor 'E' circuit.
  6. Aftermarket floor mats or debris interfering with the pedal mechanism and causing erratic sensor movement.

How to diagnose and fix it

  1. Inspect the accelerator pedal and throttle body connectors for corrosion, water, or loose pins, and clean or reseat them as needed.
  2. Wiggle-test the sensor 'E' circuit wiring while watching live data on a scan tool to reproduce the intermittent fault.
  3. Check the sensor 'E' signal voltage with a multimeter or oscilloscope for dropouts or spikes as the pedal is slowly cycled.
  4. Compare sensor 'E' readings with the other throttle/pedal sensor tracks to confirm which circuit is erratic.
  5. Repair any damaged wiring or replace the affected connector terminal before condemning the sensor.
  6. Replace the accelerator pedal position sensor assembly or throttle body only after electrical tests confirm the sensor itself is faulty.
  7. Clear the code and perform a throttle relearn or idle relearn procedure if required by the vehicle manufacturer.

Intermittent faults hide in the wiring

  • A loose ground connection for the pedal sensor or throttle body can create intermittent voltage drops that mimic a failing sensor 'E' circuit.
  • Aftermarket floor mats that curl up under the pedal can physically bump the sensor and set P2129 without any electrical defect.
  • The code can be stored by a brief glitch that never repeats, so clearing it and test-driving may be the only way to confirm a hard failure.
  • On some vehicles, a weak battery or charging system ripple can cause the computer to misread the sensor 'E' signal as intermittent.
  • Technicians often replace the pedal assembly only to find the real fault was a chafed wire in the harness near the firewall.

Can I keep driving with P2129?

You can usually drive the vehicle to a repair shop, but avoid heavy acceleration and be prepared for the engine to enter limp mode without warning. If the pedal feels unresponsive or the vehicle surges, stop driving and have it towed to prevent a loss of control.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage