P0740

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)
^ P0741: Abnormality in lockup function
^ P0746: Abnormality in hydraulic control system function
^ P0841: Abnormality in line pressure sensor function

Sensor (The sensor below is determined to be normal)
^ Not applicable

LOGIC FLOW CHARTS (Monitor Sequence)

Logic Flow Charts (Monitor Sequence):

^ Engine speed: 450 r/min or more
^ Transmission fluid temperature: 20°C (68°F) or more.
^ Transmission fluid temperature: 99°C (210°F) or more.

DTC SET CONDITIONS

Judgement Criteria
^ Monitored current [target current: 750 mA or more]: 400 mA or less. (5 seconds)
^ Lock-up solenoid valve circuit: ground short. (1 second)

OBD-II DRIVE CYCLE PATTERN
All the conditions below continue for 6 seconds.
^ Transmission range switch: D
^ Vehicle speed: 10 km/h (6.2 mph) or more
^ Throttle position: 1/8 or more

PROBABLE CAUSES
^ Malfunction of valve body assembly (Faulty lockup solenoid valve)
^ Damaged wiring harness and connectors
^ Malfunction of TCM

DIAGNOSTIC PROCEDURE

STEP 1. M.U.T.-III 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.

Q: Is the check result normal?
YES: Intermittent malfunction
NO: Go to Step 2.

STEP 2. Check the following connector:
^ C-41 TCM connector
^ B-08 CVT assembly connector

Check the terminals for a contact status problem and internal short circuit.

Q: Is the check result normal?
YES: Go to Step 3.
NO: 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-41 TCM connector (terminal No.3) and B-08 CVT assembly connector (terminal No.3)

Q: Is the check result normal?
YES: Go to Step 4.
NO: Repair the wiring harness.

STEP 4. Lockup solenoid valve single unit check

Q: Is the check result normal?
YES: Go to Step 5.
NO: Replace the valve body assembly.

STEP 5. Symptom recheck after erasing diagnosis code

Q: Is the check result normal?
YES: Intermittent malfunction
NO: Replace TCM.