P1778

DTC P1778 STEP MOTOR - FUNCTION





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




CONSULT-III Reference Value









On Board Diagnosis Logic
- This is an OBD-II self-diagnostic item.
- Diagnostic trouble code "P1778 STEP MOTR/FNC" with CONSULT-III is detected under the following conditions.
- When not changing the pulley ratio according to the instruction of TCM.




Possible Cause
Step motor




DTC Confirmation Procedure

CAUTION:
- Always drive vehicle at a safe speed.
- Before starting "DTC Confirmation Procedure", confirm "Hi" or "Mid" or "Low" fixation by "PRI
SPEED" and "VEHICLE SPEED" on "DATA MONITOR MODE".
- If hi-geared fixation occurred, go to "Diagnosis Procedure".

NOTE:
If "DTC Confirmation Procedure" has been previously performed, always turn ignition switch OFF and wait at least 10 seconds before performing the next test.
After the repair, touch "ERASE" on "SELF-DIAG RESULTS" and then perform the following procedure to confirm the malfunction is eliminated.

WITH CONSULT-III
1. Turn ignition switch ON and select "DATA MONITOR" mode for "TRANSMISSION" with CONSULT-III.
2. Make sure that output voltage of CVT fluid temperature sensor is within the range below.
ATF TEMP SEN: 1.0 - 2.0 V
If out of range, drive the vehicle to decrease the voltage (warm up the fluid) or stop engine to increase the voltage (cool down the fluid)
3. Select "DATA MONITOR" mode for "TRANSMISSION" with CONSULT-III.
4. Start engine and maintain the following conditions for at least 30 consecutive seconds.
TEST START FROM 0 km/h (0 MPH)
CONSTANT ACCELERATION: Keep 30 sec or more
VEHICLE SPEED: 10 km/h (6 MPH) or more
ACC PEDAL OPEN: More than 1.0/8
RANGE: "D" position
ENG SPEED: 450 rpm or more
5. If DTC is detected, go to "Diagnosis Procedure".

WITH GST
Follow the procedure "WITH CONSULT-III".




Diagnosis Procedure
1.CHECK STEP MOTOR
With CONSULT-III
It is monitoring whether "GEAR RATIO: 2.34 - 0.39" changes similarly to "STM STEP: 0 - 177" by DATA MONITOR mode. Refer to CONSULT-III Function (Transmission).
Without CONSULT-III
Inspect the engine speed (rise and descend), vehicle speed, throttle position, and check shift change. Refer to Vehicle Speed When Shifting Gears.
OK or NG
OK >> INSPECTION END
NG >> Replace the transaxle assembly. Refer to .