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DTC P1777: Malfunction of Stepper Motor
 
 

 
 
 
 
DIAGNOSTIC FUNCTION
TCM conducts fault detection by monitoring the voltage of each coil for stepper motors.
 
 
DESCRIPTIONS OF MONITOR METHODS
  • The specified voltage is not applied to each coil for stepper motors for 0.2 second because of an open or short circuit.
 
 
MONITOR EXECUTION
  • Continuous
 
 
MONITOR EXECUTION CONDITIONS (OTHER MONITOR AND SENSOR)
Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
  • P0715: Malfunction of primary pulley speed sensor
  • P0740: Malfunction of lockup solenoid valve
  • P0745: Malfunction of line pressure solenoid valve
  • P0840: Malfunction of secondary pressure sensor
Sensor (The sensor below is determined to be normal)
  • Primary pulley speed sensor
  • Secondary pressure sensor
 
 
LOGIC FLOW CHARTS (Monitor Sequence)
 
 
DTC SET CONDITIONS
Judgment Criteria
  • Stepping motor activation command (ON voltage): 2.8 volts or less. (0.2 second)
  • Stepping motor activation command (OFF voltage): More than 2.8 volts. (0.2 second)
 
 
OBD-II DRIVE CYCLE PATTERN
Ignition switch: ON (start the engine and keep it for 10 seconds or more)
 
 
PROBABLE CAUSES
  • Malfunction of valve body assembly (Faulty stepper motor)
  • Damaged wiring harness and connectors
  • Malfunction of TCM
 
 
DIAGNOSIS
STEP 1. Check the following connector:
  • B-120 CVT assembly connector
  • C-130 TCM connector
Check the terminals for a contact status problem and internal short circuit.
Is the check result normal?
Go to Step 2.
Repair the defective connector.
 
STEP 2. Check for open circuit and short to ground in the wiring harness between the TCM connector and the stepper motor.
  • Between C-130 TCM connector (terminal No.40) and body ground
  • Between C-130 TCM connector (terminal No.41) and body ground
  • Between C-130 TCM connector (terminal No.51) and body ground
  • Between C-130 TCM connector (terminal No.52) and body ground
OK: Resistance value is approximately 15 Ω.
Is the check result normal?
Go to Step 4.
Go to Step 3.
 
STEP 3. Check for open circuit and short to ground in the wiring harness between TCM and the stepper motor
  • Between C-130 TCM connector (terminal No.40) and B-120 CVT assembly connector (terminal No.8)
  • Between C-130 TCM connector (terminal No.41) and B-120 CVT assembly connector (terminal No.9)
  • Between C-130 TCM connector (terminal No.51) and B-120 CVT assembly connector (terminal No.10)
  • Between C-130 TCM connector (terminal No.52) and B-120 CVT assembly connector (terminal No.11)
Check that there is no continuity in both sides of the connectors and that no short circuit is present between the connectors and the body ground.
Is the check result normal?
Replace the valve body assembly.
Repair the wiring harness.
 
STEP 4. Symptom recheck after erasing diagnostic trouble code
Is the check result normal?
Intermittent malfunction
Replace TCM.