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DTC codes / GM codes / P1122

P1122 · GMThrottle Position Sensor Out of Range

P1122 on a GM vehicle means the powertrain control module (PCM) has detected a throttle position sensor (TPS) signal that falls outside the expected voltage range for the current operating conditions. The PCM compares the TPS voltage against a calculated model and sets this code when the signal is too high, too low, or inconsistent with the commanded throttle angle.

SystemPowertrain
Code typeGM specific
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering

Symptoms you may notice

  • The check engine light (malfunction indicator lamp) illuminates, often with no other noticeable symptoms.
  • The engine may idle erratically or at an incorrect speed, sometimes surging or stalling.
  • Acceleration may feel sluggish or unresponsive, as if the throttle is not responding properly.
  • The transmission may shift harshly or at the wrong time due to incorrect throttle position data.
  • In some cases, the vehicle may enter limp mode, limiting engine power to protect the drivetrain.

Common causes, most likely first

  1. A faulty throttle position sensor (TPS) that has worn out or developed a dead spot in its resistive track.
  2. Damaged or corroded wiring in the TPS circuit, including the reference voltage, signal, or ground wires.
  3. Loose or dirty electrical connectors at the TPS or PCM, causing intermittent signal loss.
  4. A binding or sticking throttle plate or accelerator pedal linkage that prevents the TPS from moving smoothly.
  5. Contamination or carbon buildup on the throttle body that restricts throttle plate movement and skews the TPS reading.
  6. A PCM software issue or internal fault that misinterprets the TPS signal (rare but possible).

How to diagnose and fix it

  1. Scan all modules for stored codes and freeze-frame data to confirm P1122 is the primary fault and not a secondary effect.
  2. Visually inspect the TPS, throttle body, and accelerator pedal linkage for binding, carbon buildup, or mechanical damage.
  3. Back-probe the TPS connector and check the reference voltage (typically 5V), signal voltage, and ground integrity with a multimeter.
  4. Perform a sweep test on the TPS signal using a scan tool or oscilloscope to look for smooth voltage changes without dropouts or spikes.
  5. Clean the throttle body and re-test; carbon buildup is a common cause of restricted movement and skewed TPS readings.
  6. If the TPS signal is erratic or out of specification, replace the TPS and clear the codes, then perform a throttle relearn procedure if required.
  7. Repair any damaged wiring or connectors, then verify the repair by test-driving the vehicle and confirming the code does not return.

TPS Signal Sweep Test Catches Intermittent Faults

  • A TPS can test fine with a multimeter at idle and wide-open throttle but still have a dead spot in the middle of its range that only a sweep test reveals.
  • Carbon buildup on the throttle plate is often overlooked as a cause of P1122 because it mechanically restricts movement and skews the TPS voltage without setting a TPS circuit code.
  • The accelerator pedal position sensor (APP) on drive-by-wire systems can mimic TPS faults, so always compare APP and TPS readings on a scan tool before replacing parts.
  • Intermittent P1122 codes are frequently caused by a chafed wire harness near the throttle body that only loses contact when the engine moves under load.
  • Replacing a TPS without checking the reference voltage can lead to repeat failures if the PCM is supplying an incorrect 5V reference due to a shorted sensor on the same circuit.

Can I keep driving with P1122?

You can usually drive the vehicle to a repair shop, but avoid aggressive acceleration or heavy loads because a faulty TPS can cause unpredictable throttle response. If the vehicle enters limp mode or stalls, pull over safely and have it towed.

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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