Code Definition

P1121 — Throttle Position lower than expected

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

About P1121

P1121 is a manufacturer-specific powertrain diagnostic trouble code recorded for Honda 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 signal or supply voltage lower than the expected operating range.

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 Throttle Position (TP) sensor reports the throttle plate angle to the Powertrain Control Module (PCM) as a varying voltage signal. DTC P1121 is a Honda specific code that sets when the PCM detects the TP sensor signal is continuously lower than expected, meaning the reported throttle angle does not agree with other inputs such as engine load, MAP, and airflow. This usually points to a TP sensor reading low, a wiring fault in the sensor circuit, or a connector problem rather than a true mechanical throttle fault. When this code is set the driver may notice rough idle, hesitation or stumble ...

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