'97 accord code 740 lockup clutch

[jerry/michele]

Had a diagnostic done after the check engine light would not go off. Got a code 740, lockup clutch. My mechanic said to go to a transmission place. He had no idea if it was a serious problem or not. The car continues to drive fine with no problems. Has anyone had experience with this problem? Is it something that can easily be fixed or can it be ignored? If you've had it fixed, what was the price?

thanks

[jeffcoslacker]

Haven't seen this problem much on Hondas. Very common on GM's. The lockup mechanically locks the two stages of the torque convertor together for a slip-free connection when cruising. Until lockup, the torque convertor functions as a hydraulic turbine, with fluid pressure on the flywheel side turning vanes in the other stage. Upon lockup, (usually above 40 mph or so, with light load) fuel efficiency rises as engine RPMs drop by a couple of hundred.

There can be several reasons for failure, from electrical (bad connection, powertrain module command fault, etc) to mechanical (bad solenoid, worn lockup clutch) to problems stemming from hydraulic causes (fluid pressure bleeding off due to faulty seal, etc).

There is a specific routine that has to be run to determine exactly what component has failed. In a GM, you can replace the solenoid and about 95% of the time that'll cure it, as it is the weak link in the system. But I don't know about on a Honda. The job can cost $400-$600 on a GM, depending on how much diagnostic time is required and the labor rate (for a solenoid replacement). If the actual TCC mechanism is bad, the tranny has to come out to R+R the torque convertor. This could get pricey.

There is also the possibility that the TCC system just got confused in an unusal driving situation, and the code was set simply because lockup didn't occur when the ECM thought it should have. In other words, it may have been a one time glitch, and is completely meaningless.

I'd have the code cleared, and if it doesn't set again, I wouldn't worry about it.