P0740 refers to a faulty lock-up control system in your automatic transmission - lock-up clutch doesn't engage.
There's the step by step way to resolve the problem. You'ld have to measure the line pressure at the lock-up control solenoid valve to find out exactly what the problem is.
Typically thre pressure should be between 120 - 130 psi at 2000 rpm. If you have none or low line pressure while in gear N or P, it could be caused by a bad torque converter, ATF pump, pressure regulator, or torque converter check valve.
If it falls within specification, you may be luck to just have to replace your lock-up control solenoid ($46 from ebay. Com)
first thing i'd do is check the fluid level.
Tuesday, June 7th, 2011 AT 5:26 AM