1998 Chrysler Town and Country OBD code P0740

That's related to the torque converter lockup clutch. Not sure if that means it isn't engaging or there is an electrical problem with the solenoid. There is a different potential code for "no drop in rpm when the clutch has been commanded to engage". If you have a tach on the dash you should see engine speed drop about 200 rpm when it engages in 3rd or 4th gear and the engine is warmed up. When cruising at a steady speed, lets say 50 mph, the rpm should increase very gradually as you increase vehicle speed to around 55 or 60 mph. If it jumps up a few hundred rpm right away, the clutch isn't locking up. A better test is to hold the road speed and gas pedal steady at highway speed, then momentarily tap the brake pedal. Engine speed should increase 200 rpm, then go back down within a couple of seconds. If it does, the lockup clutch is working.