P2B81: A SENT status problem in bank 1 wastegate feedback

P2B81 is labelled wastegate position sensor A performance in the dictionary. The cited GM row is more specific: it checks whether the status and communication nibble for channel 1 of the bank 1 wastegate position sensor is valid. SENT carries diagnostic information as well as a position value.

A plausible number is not enough

The source permits the check when the received message value lies between 1 and 4,088 and the separate SENT sensor-error status is false. The fault criterion is an invalid status/communication nibble, qualified for 500 milliseconds. Its continuation appears on the following page.

Those conditions explain why a position number within an expected numerical range cannot by itself clear this concern. The message's diagnostic status can be invalid even when the data field is not at either excluded endpoint. Conversely, a separately reported sensor error can prevent this particular check from operating.

Keep protocol evidence with position data

Retain the status-nibble result, message value and related sensor-error state if the diagnostic equipment exposes them. Investigating only mechanical wastegate travel would ignore the actual failure decision described in this row. The summary does not, however, identify the electrical origin of an invalid nibble or give a waveform test procedure.

A meaningful verification confirms valid status during an eligible message stream, not simply reasonable boost output. The source lists a two-trip response but supplies no universal vehicle mapping. Match the controller and sensor interface before using this monitor description to guide physical tests.

Source and applicability

2025 GM 07A-2 documented monitor only; module and calibration applicability must be matched to the vehicle. The application-matrix filename join remains unresolved; no model or engine fitment is inferred. GM PDF, page 862. GM PDF, page 863.