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DTC codes / GM codes / P1288

P1288 · GMAccelerator Pedal Position Sensor 3 Circuit High Voltage

P1288 on a GM vehicle means the engine control module (ECM) has detected an abnormally high voltage signal on the accelerator pedal position sensor 3 circuit, which is one of the redundant sensors inside the drive-by-wire pedal assembly. The ECM compares this signal against the other pedal sensors and expects a specific voltage range; a high voltage indicates an open circuit, a short to voltage, or a faulty sensor.

SystemPowertrain
Code typeGM specific
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering (injector circuits)

Symptoms you may notice

  • The check engine light or reduced engine power message illuminates on the dashboard.
  • The accelerator pedal may feel unresponsive or the engine may idle at a fixed elevated speed.
  • The vehicle may enter limp mode, limiting speed to a low threshold.
  • In some cases, the driver notices no symptoms besides the warning light.
  • Intermittent hesitation or surging may occur if the fault is a loose connection.
  • The cruise control system may become inoperative.

Common causes, most likely first

  1. A faulty accelerator pedal position sensor 3 inside the pedal assembly.
  2. An open circuit or high resistance in the signal wire between the sensor and the ECM.
  3. A short to voltage on the sensor signal circuit, often from chafed wiring near the pedal or under the dash.
  4. Corroded or loose terminals at the pedal connector or ECM connector.
  5. A damaged or misadjusted accelerator pedal assembly.
  6. A rare internal ECM fault on the sensor input channel.

How to diagnose and fix it

  1. Scan all modules for stored codes and freeze-frame data to confirm P1288 is current and not history.
  2. Visually inspect the accelerator pedal connector and wiring for corrosion, chafing, or loose pins.
  3. Backprobe the sensor 3 signal wire at the pedal connector and compare voltage to the service manual specification while slowly pressing the pedal.
  4. Check for a short to voltage on the signal circuit by measuring voltage with the sensor disconnected and the key on.
  5. Perform a wiggle test on the harness while monitoring sensor voltage to reveal intermittent opens.
  6. If wiring and connectors are good, replace the accelerator pedal assembly and clear codes.
  7. After repair, clear codes and perform a throttle relearn or idle relearn procedure if required by the model.

Why P1288 is often a wiring fault

  • The accelerator pedal position sensor 3 is a redundant signal, and its high voltage often results from a broken ground or reference wire rather than a failed pedal.
  • A common misdiagnosis is replacing the pedal assembly when the real problem is a chafed wire under the dashboard near the steering column.
  • P1288 can be set by a low battery or charging system issue that causes the ECM to see an out-of-range voltage momentarily.
  • On some GM trucks and SUVs, the pedal connector can become loose from repeated kicking or floor mat interference.
  • The code does not always mean the pedal is bad; always check the sensor 3 circuit with a multimeter before condemning parts.

Can I keep driving with P1288?

If the vehicle is in reduced power mode, avoid highway driving and seek service promptly; if only the warning light is on with normal drivability, you can drive cautiously to a repair shop but avoid aggressive acceleration.

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 GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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