P1777

DTC P1777 STEP MOTOR - CIRCUIT

Description
- The step motor changes the step WITH turning 4 coils ON/OFF according to the signal from TCM. As a result, the flow of line pressure to primary pulley is changed and pulley ratio is controlled

CONSULT-III Reference Value:

On Board Diagnosis Logic
- This is an OBD-II self-diagnostic item.
- Diagnostic trouble code P1777 STEP MOTR CIRC with CONSULT-III is detected under the following conditions.
- When operating step motor ON and OFF, there is no proper change in the voltage of TCM terminal which corresponds to it.

Possible Cause
- Step motor
- Harness or connectors
(Step motor circuit is open or shorted.)

DTC Confirmation Procedure

CAUTION: Always drive vehicle at a safe speed.

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. Drive vehicle for at least 5 consecutive seconds.
3. If DTC is detected, go to CVT-154, "Diagnostic Procedure".

WITH GST
Follow the procedure WITH CONSULT-III.

CVT-STM-01:

Wiring Diagram - CVT - STM

TCM TERMINALS AND REFERENCE VALUES
Refer to CVT-49, "TERMINALS AND REFERENCE VALUES FOR TCM". Pinout Values and Diagnostic Parameters

Diagnostic Procedure
1. CHECK INPUT SIGNALS

WITH CONSULT-III
1. Start engine.
2. Select SELECTION FROM MENU in DATA MONITOR mode for TRANSMISSION with CONSULT-III.
3. Start vehicle and read out the value of STM STEP, SMCOIL A, SMCOIL B, SMCOIL C, and SMCOIL D.





OK or NG
OK >> GO TO 4.
NG >> GO TO 2.

2. CHECK HARNESS BETWEEN TCM AND STEP MOTOR
1. Turn ignition switch OFF.
2. Disconnect CVT unit connector and TCM connector (A).








3. Check continuity between TCM connector (A) terminals and CVT unit harness connector (B) terminals.
4. If OK, check harness for short to ground and short to power.
5. If OK, check continuity between body ground and CVT assembly.
6. Reinstall any part removed.
OK or NG
OK >> GO TO 3.
NG >> Repair open circuit or short to ground or short to power in harness or connectors.

3. CHECK STEP MOTOR
Check step motor. Refer to CVT-155, "Component Inspection".
OK or NG
OK >> GO TO 4.
NG >> Repair or replace damaged parts.

4. CHECK DTC
Perform CVT-152, "DTC Confirmation Procedure".
OK or NG
OK >> INSPECTION END
NG >> GO TO 5.

5. CHECK TCM
1. Check TCM input/output signals. Refer to CVT-49, "TCM Input/Output Signal Reference Values". Pinout Values and Diagnostic Parameters
2. If NG, re-check TCM pin terminals for damage or loose connection with harness connector.
OK or NG
OK >> INSPECTION END
NG >> Repair or replace damaged parts.

Component Inspection
STEP MOTOR
1. Turn ignition switch OFF.
2. Disconnect CVT unit harness connector.








3. Check resistance between CVT unit harness connector terminals and ground.
4. If NG, replace the transaxle assembly.