P0849: Pressure sensor B intermittency can be a clutch-2 zero-offset check

P0849 is generically described as pressure sensor B circuit intermittent. The GM implementation cited here checks clutch 2 pressure-sensor drift outside an allowed window during a defined zero-pressure condition. That specific strategy is more informative than assuming every occurrence means a loose wire.

A zero-pressure opportunity exposes offset

The monitor evaluates the absolute raw clutch 2 pressure against a calibrated drift threshold. It also considers whether valid raw samples were obtained during the expected zero-pressure condition. The numerical drift limit and sample rules are referenced in summary attachments rather than printed in this row.

The controller must have been awake for more than 20 milliseconds, the application must not be in bypass state, and the electrical pressure-sensor diagnosis must indicate OK. A code-clear event is excluded. These qualifications separate the drift check from a basic open-circuit diagnosis.

Preserve raw pressure and the zero condition

A pressure reading is meaningful for this monitor only when the documented clutch-zero-pressure condition is satisfied. An ordinary loaded-clutch value cannot be judged as an offset sample.

The source does not prove that a mechanically leaking clutch or an intermittent connector caused the result. Confirm the calibration’s P0849 implementation and zero-pressure criteria before selecting a service test. The article explains the supported drift-monitor behavior while leaving the exact attachment-defined window and sample validation to the applicable transmission information.

Source and applicability

This explanation covers the cited GM monitor, not every vehicle carrying this code. The application-matrix filename does not resolve cleanly to this file, so no model or engine fitment is assigned. GM diagnostic table, PDF page 977.