P073B: Sixth gear stuck means repeated failure to disengage it

P073B identifies the sixth-gear stuck condition. The GM table bases the diagnosis on failed disengagement attempts, which differs from a gear-ratio calculation or an inability to enter sixth in the first place.

A qualified neutral transition fails

The sixth-gear disengagement request must be present and the actuation active. The row identifies shift-fork position sensor 3 for an electrical or consistency-fault path. It also monitors whether required state transitions fail to occur before their calibrated timeout.

System pressure must exceed 4.5 bar, and the application must not be in its error or bypass state. Confirmation requires at least four failed disengagement attempts. The presence of these conditions prevents interpreting one vague shift complaint as the entire diagnostic event.

Preserve sixth-gear-specific history

Record which gear was being left, the neutral target, sensor-3 status and the state where the sequence stopped. The same physical feedback branch appears in another documented gear sequence, but that does not make its successful operation in one event proof that the sixth-gear transition passed.

The source does not locate a stuck mechanical part or identify the failed electrical component. It also delegates exact transition and timeout settings to calibration attachments. Follow the applicable transmission diagnostic process rather than forcing repeated shifts to reach the count. The monitor narrows the event to failed sixth-gear disengagement and leaves cause localization to further evidence.

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 1041.