P1778 Volvo Transmission Reverse I/P Circuit Malfunction

The step motor’s 4 aspects of ON/OFF change according to the signal from Transmission Control Module (TCM). As a result, the flow of line pressure to primary pulley is changed and pulley ratio is controlled. This diagnosis item detects when electrical system is OK, but mechanical system is NG. This diagnosis item detects when the state of the changing the speed mechanism in unit does not operate normally.