Code Definition

P0721 — Output Speed Sensor Range/Performance

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P0721

P0721 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0721 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.

Because P0721 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The P0721 code is set when the Engine Control Module (ECM) or Transmission Control Module (TCM) identifies an issue with the range or performance of the output speed sensor. This sensor is critical for measuring the speed of the transmission's output shaft, which is essential for appropriate gear shifting and overall transmission operation. The code suggests that the sensor's output is either not within the expected range or is performing inconsistently. Such discrepancies can result in improper transmission shift timing, erratic shifts, or in some cases, cause the transmission to go into a fa...

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