Code Definition

P1128 — Throttle Control Motor Lock

System: Powertrain  |  Type: Manufacturer-Specific  |  Make: Lexus

About P1128

P1128 is a manufacturer-specific powertrain diagnostic trouble code recorded for Lexus vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

P1128 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

On this Lexus electronic throttle control system the Engine Control Module (ECM) drives the throttle control motor and monitors throttle plate movement through the throttle position sensor. DTC P1128 sets when the ECM commands the motor to move the throttle but the throttle position does not change as expected, indicating the throttle control motor or throttle valve is mechanically locked. Common triggers are heavy carbon buildup binding the throttle plate, a seized motor or gear train, or a foreign object jamming the throttle bore. When this code is stored the ECM enters a fail safe limp mode...

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