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DTC P0740: Malfunction of Lockup Solenoid Valve
 
 

 
 
 
 
DIAGNOSTIC FUNCTION
TCM determines malfunction by detecting the abnormality in the lockup solenoid valve.
 
 
DESCRIPTIONS OF MONITOR METHODS
  • Specified amount of current is not flown to the lockup solenoid valve 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
  • 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-Output Open Circuit/Shorted-high)
 
 
LOGIC FLOW CHARTS (Monitor Sequence-Output Shorted Low)
 
 
DTC SET CONDITIONS
Check Conditions
  • Ignition switch: ON
Judgment Criteria
  • Monitored current [target current: 750 mA or more]: 400 mA or less. (5 seconds)
  • Monitored current: 1.34 A or more (1 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 lockup solenoid valve)
  • Damaged wiring harness and connectors
  • Malfunction of TCM
 
 
DIAGNOSIS
STEP 1. Scan tool data list
  • Item 31: LU solenoid output current
  • Item 30: LU solenoid monitor current
OK: Check if the output current and monitoring current differ largely.
Is the check result normal?
Intermittent malfunction
Go to Step 2.
 
STEP 2. Check the following connector:
  • C-131 TCM connector
  • A-16 Intermediate connector
  • B-120 CVT assembly connector
Check the terminals for a contact status problem and internal short circuit.
Is the check result normal?
Go to Step 3.
Repair the defective connector.
 
STEP 3. Check for open circuit and short to ground in the wiring harness between the TCM connector and the CVT assembly connector.
Between C-131 TCM connector (terminal No.3) and B-120 CVT assembly connector (terminal No.3)
Is the check result normal?
Go to Step 4.
Repair the wiring harness.
 
STEP 4. Lockup solenoid valve single unit check
Refer to .
Is the check result normal?
Go to Step 5.
Replace the valve body assembly.
 
STEP 5. Symptom recheck after erasing diagnostic trouble code
Is the check result normal?
Intermittent malfunction
Replace TCM.