Code Definition

P1120 — Throttle Position Sensor 1 Circuit

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

About P1120

P1120 is a manufacturer-specific powertrain diagnostic trouble code recorded for GM vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1120 is stored, the module has detected 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.

P1120 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

This DTC sets when the Engine Control Module (ECM) detects a fault in the signal circuit from Throttle Position Sensor 1 (TPS1), typically used in electronic throttle control (ETC) systems. The TPS1 provides a voltage signal proportional to throttle plate position, and the ECM continuously monitors this signal and compares it against expected values and the redundancy from other TPS circuits. If the signal is missing, erratic, or out of range, the ECM logs P1120. When this code sets the ECM usually forces a reduced power limp mode, so the driver may notice sluggish acceleration, limited thrott...

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