What causes a P0729 code?

P0729 can be triggered by several issues — see the verified probable causes and step-by-step diagnostics shared by mechanics and owners on OBDIY.

Can I drive with a P0729 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P0729 active.

Follow the step-by-step diagnostic on this page, then read the verified fixes contributed by other Heavy Truck owners — the answer marked "Verified Cause" worked for the original poster.

OBDIY

OBD-II

P0729

P0729 Gear 6 Incorrect Ratio - Heavy Duty Transmission

What it means

The Transmission Control Module (TCM) has detected a mismatch between engine RPM/input shaft speed and output shaft speed while the transmission is commanded into 6th gear.