Welcome to 2carpros. Here are the diagnostic procedures. Hope it is helpful.
DTC P0740/40: LOCK-UP CONTROL SYSTEM
DO NOT perform this DTC test until all other DTCs have been repaired first.
1. Using scan tool, retrieve A/T freeze data. Clear DTCs and road test vehicle under same conditions freeze data was recorded. If DTC returns, go to next step. If DTC does not return, problem is intermittent. Check transaxle and PCM connections.
2. Using scan tool, check for any other DTCs. If any other DTCs are present, repair those DTCs first and recheck for DTC P0740/40. If no other DTCs are present, go to next step.
3. Measure clutch pressure at each clutch pressure tap on transaxle. If all clutch pressures are within specification, go to next step. If any clutch pressure is not within specification, repair hydraulic system as necessary.
4. Replace lock-up control solenoid assembly and A/T clutch pressure control solenoid valve "C". Turn ignition off and clear codes. Ensure engine coolant temperature is greater than 176 F (80 C). Road test vehicle at 55 MPH for more than one minute. Recheck DTCs. If DTC P0740/40 returns, replace transaxle and torque converter. If DTC P0740/40 does not return, system is okay.
Thursday, November 4th, 2010 AT 7:19 AM