DTC Advanced Diagnostics: P0721: General Description

Courtesy of HONDA, U.S.A., INC.

The countershaft speed sensor is attached to the outside of the transmission housing. The countershaft speed sensor generates different frequency pulse signal depending on the rotating speed of the countershaft driven gear. The pulse signal is transmitted to the transmission control module (TCM) and used for measurement of the countershaft speed. When there is a missing pulse while the countershaft is rotating which occurs by open circuit, intermittent open circuit, and short circuit, the TCM detects as a malfunction. The countershaft speed sensor speed and the mainshaft speed sensor speed are compared, and if there is an abnormality in detected sensor speed ratio for a specified time, the TCM detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type