The step motor has four aspects that have some variations according to the signal provided by the TCM (Transmission Control Module). As a result, the flow of line pressure to the primary pulley changes, and the pulley ratio is controlled. With this diagnosis, it is detected when the electrical system is working properly, but there are instabilities from the mechanical system. It also detects when the state of the speed change mechanism in the unit shows irregularities in its performance.
OBDII fault code P1778 is set on Infiniti and Nissan vehicles when there is a big difference between the number of steps of the stepper motor and the actual transmission ratio.
OBD2 DTC P1778 is stored for the following reasons:
Stepper motor wiring may be damaged.
Stepper motor circuit electrical connections may be faulty.
The stepper motor may be damaged.
Possible solutions of the DTC code P1778
Steps to fix the P1778 OBDII diagnostic code are:
To begin the diagnosis, we recommend you consult the TSBs. They contain very useful information.
Check the cables related to the stepper motor and make sure that all of them are in optimal condition for proper operation. If you discover common damage such as wear and tear or burns, make the appropriate repairs.
Using the appropriate tools, check if the stepper motor voltages match the manufacturer's specifications. If you discover deficiencies that cause an open circuit, make the appropriate corrections.
Check the integrity of the stepper motor. Take into account the diagnostic steps recommended by the manufacturer, and if you detect damage to the motor, replace it.