P0734: Fourth-gear ratio verification must include the end of the shift

P0734 is the fourth-gear entry in Ford's general ratio monitor. A useful interpretation starts by separating the shift into fourth gear from the interval when fourth is commanded and should be established. The source's eligibility requirements make that separation explicit.

The monitor needs a valid operating window

Ford lists a non-shifting interval longer than half a second along with torque, throttle and speed requirements. Forward range must have remained selected for more than eight seconds in the typical example. These conditions prevent a diagnostic capture from being judged without its operating context.

The stated forward-ratio failure exceeds 30 rpm of error for more than 2.5 seconds and must repeat six times across key cycles, without solenoid faults being detected. The evidence therefore needs both magnitude and persistence; a peak seen at one transition is not the complete test.

Use the transmission's own meaning

The TR9070 table calls P0734 an unknown fourth-gear state; P074C separately identifies failure to engage fourth and P072F failure to disengage it. It would be misleading to select one of those failure directions solely from P0734.

Preserve commanded gear, shift status and the relevant shaft-speed traces together. Companion electrical faults may affect whether the ratio evidence is trustworthy or whether the documented check can be interpreted. The summary does not supply a universal fourth-gear clutch assignment, so component tests and repair choices require the exact transmission procedure.

Source and applicability

Ford 2024–2025 gasoline OBD operation summary, July 16 2024 revision; only the cited monitor and transmission architectures. No individual vehicle fitment or universal calibration is inferred. Ford PDF, page 152. Ford PDF, page 153. Ford PDF, page 167.