Code Definition

P1121 — Accelerator Pedal Position Sensor Range/Performance Problem

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

About P1121

P1121 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.

When P1121 is stored, the module has detected a plausibility fault — the measured value is in the electrical range but is not consistent with expected operating behaviour; and a sensor-related fault — the reported value from the named sensor is out of spec.

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.

P1121 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

The Engine Control Module (ECM) monitors the Accelerator Pedal Position (APP) sensor to determine driver demand and command the electronic throttle body accordingly. DTC P1121 sets when the ECM detects that the APP sensor signal is outside the expected range or does not correlate correctly between its redundant signal circuits during pedal operation. The APP sensor assembly contains two independent sensor elements that produce separate but proportional voltage signals so the ECM can cross check pedal position for plausibility. When this code is set the vehicle commonly enters a reduced power o...

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