Hello , I have a code P0740 in my 96 accord 4 cyl v tech,,transmission was rebuilt 2/3 years ago,,now I have a code p0740 pop up today. Fluid is full and looks like new,,no burnt smell..research shows tcc lock up switch circuit open or shorted. What is the fix?? Any ideas where to start looking,,Solenoid packs?? which one?? Thanks in advance.

 

A faulty lockup system isn't the end of the world. The lockup system is that slight drop in rpm you get when you are going a constant speed.

The shop manual has a procedure where you test the hydraulic pressure in the line and 1st, 2nd, 3rd, and 4th clutches. It doesn't look too difficult, but you would need a high pressure gauge set to do this test.

The next step is to check the resistance on the lock-up solenoid. Find what the part looks like on ebay. The lockup solenoid sits on top of the transmission near a radiator hose and is easy to see/access. Unplug the solenoid which has 2 wires going to it (. Measure the resistance from one wire to body ground on the solenoid side of the harness. Repeat the test on the other wire. The resistance should be 12-24 ohms.

You can also apply 12V to each solenoid wire on the solenoid side of the harness and listen for it to click. I'd suggest using a wire with an inline fuse as a precaution. Make sure you apply voltage to the solenoid part of the wiring and not the engine harness. That could damage the PCM.

The lockup solenoid also has a screen on the gasket that could get clogged. You can unbolt the solenoid and clean any debris caught in the screen and in the solenoid. Use something like throttle body cleaner that is safe for electronics as harsher cleaners can damage the electronics.

The other possibility is the wiring leading to the solenoid or possibly a bad PCM. There are some voltage drop tests you can try that could help identify an issue. We can give you more details if you need them.

 

Thanks for the reply,,Ill look tomorrow and attempt to clean and test.. Pick and pull is close by,,gonna see if I can grab a spare..