Code Definition

P1121 — Throttle Position Sensor Inconsistent with Mass Air Flow Sensor

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

About P1121

P1121 is a manufacturer-specific powertrain diagnostic trouble code recorded for Ford 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; 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 P1121 code sets when the PCM detects that the Throttle Position Sensor signal and the Mass Air Flow sensor reading do not agree as expected. The PCM continuously cross checks throttle angle against measured airflow, since opening the throttle should produce a matching rise in airflow. When the two disagree beyond the allowed window, for example a large throttle opening with little airflow change or the reverse, the PCM sets this code. The fault can lie in either sensor, in the intake system between them, or in their wiring, and it may show as hesitation, surging, incorrect fuelling, or red...

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