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DTC codes / Mazda codes / P1122

P1122 · MazdaThrottle Position Stuck Closed

P1122 on Mazda vehicles means the powertrain control module (PCM) has detected that the throttle position sensor signal remains at or near the closed-throttle voltage even when the engine is running and the throttle plate should be open. The PCM compares the throttle position sensor (TPS) voltage against expected values from the mass airflow (MAF) sensor and engine speed, and it sets this code when the TPS signal stays stuck at the closed position for longer than a calibrated time.

SystemPowertrain
Code typeMazda specific
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering

Symptoms you may notice

  • The check engine light illuminates, and in many cases there are no other noticeable symptoms besides the warning light.
  • The engine may idle poorly or stall immediately after startup because the PCM cannot correctly calculate fuel delivery.
  • Acceleration feels flat or sluggish, as the PCM may limit fuel and timing based on a false closed-throttle signal.
  • The transmission may shift harshly or hold gears longer than normal because throttle position is a key input for shift scheduling.
  • A rough or surging idle can occur if the TPS signal intermittently sticks closed while the engine is running.

Common causes, most likely first

  1. A faulty throttle position sensor that has worn internally and no longer produces a rising voltage as the throttle opens.
  2. A sticking or binding throttle plate or throttle body linkage that prevents the throttle from opening fully, keeping the TPS at its closed position.
  3. Damaged or corroded wiring in the TPS circuit, including a short to ground on the signal wire that holds the voltage low.
  4. A poor electrical connection at the TPS connector or at the PCM, causing an intermittent or permanently low signal.
  5. Carbon buildup on the throttle body bore or plate that restricts movement and keeps the TPS in the closed range.
  6. A PCM internal fault that misinterprets a valid TPS signal, although this is far less common than sensor or wiring issues.

How to diagnose and fix it

  1. Connect a scan tool and read live throttle position sensor voltage while slowly opening the throttle by hand; a healthy sensor should show a smooth increase from about 0.5 to 4.5 volts.
  2. Visually inspect the throttle body and throttle plate for carbon buildup or mechanical binding, and clean the bore with throttle body cleaner if contamination is present.
  3. Inspect the TPS connector and the wiring harness for corrosion, chafing, or a short to ground on the signal wire, repairing any damaged sections.
  4. Backprobe the TPS signal wire at the PCM and compare it with the reading at the sensor to rule out a wiring fault between the two points.
  5. Replace the throttle position sensor if the voltage signal is erratic, stuck, or does not increase smoothly through the throttle range.
  6. Clear the diagnostic trouble codes and perform a throttle body calibration or idle relearn procedure as required for the specific Mazda model.
  7. Road test the vehicle and verify that the TPS voltage tracks throttle movement correctly and that P1122 does not return.

Why P1122 Is Often a Wiring Fault

  • A short to ground on the TPS signal wire will hold the voltage near the closed-throttle value and set P1122 even when the sensor itself is perfectly good, so always check the harness before replacing parts.
  • Carbon buildup on the throttle plate is a common cause on higher-mileage Mazda engines because it physically prevents the plate from opening fully, making the TPS report a closed throttle when the driver is accelerating.
  • Technicians sometimes replace the TPS only to find the code returns because the throttle body was not cleaned or the connector pins were spread and making poor contact.
  • P1122 can be set by a sticking throttle cable or cruise control actuator on older Mazda models, so check that the throttle plate moves freely by hand before condemning the sensor.
  • A failing mass airflow sensor can cause the PCM to set P1122 indirectly if the airflow reading does not match the expected value for a closed throttle, so review freeze-frame data before ordering parts.

Can I keep driving with P1122?

You can drive the vehicle to a repair shop, but avoid heavy acceleration and highway merging because the engine may lack power and the transmission may shift unpredictably. If the engine stalls or idles very poorly, stop driving and have the vehicle towed to prevent a safety hazard.

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

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