Code No. P1778: Malfunction of Stepper Motor Function

DIAGNOSTIC FUNCTION

CVT-ECU conducts the fault detection of the stepper motor by comparing the target value of the primary pulley speed with the actual value. (Target value: Actual secondary pulley speed multiplied by gear ratio corresponding to stepper motor position) (Actual measurement value: Actual primary pulley speed)

JUDGEMENT CRITERIA

The difference between the target value of the primary pulley speed and the actual measurement value is greater than the standard value, the difference between the target gear ratio and the actual gear ratio is 0.3 or greater, and this status continues for 5 seconds.

PROBABLE CAUSES

Malfunction of CVT-ECU
Malfunction of valve body assembly (Faulty stepper motor)

DIAGNOSTIC PROCEDURE

STEP 1. Check other diagnosis codes.

Q. Are other diagnosis codes set?

	Carry out the appropriate troubleshooting.

	Go to Step 2.

STEP 2. Symptom recheck after erasing diagnosis code

Q. Is the check result normal?

	Intermittent malfunction

	Replace the CVT-ECU, and then go to Step 3.

STEP 3. Retest the system.

Q. Is the check result normal?

	The inspection is complete.

	Replace the valve body assembly.