so the CEL came on today and is showing code 0740,I am guessing bad solenoid.
good thing is a new transmission and is under warranty, they probably use the same solenoid from the original tranny.
The car drive perfectly fine the transmission is perfect so
what is the function of the solenoid?

 

It could be a couple of other things beside a bad solenoid.

 

didnt you just get it replaced? Luckily for you its under warranty.
I still didnt get a chance to clean my linear solenoid. Its too cold outside.

 

yeah it was the upper solenoid and operantly they did use the old one from the original transmission since it was good.

It is a brand new transmission and is under warranty for 2 or 3 yrs I have to read the papers again.
What is the upper solenoid for? if it wasn't for the CEL I would have never notice the solenoid was bad.

 

the top solenoid, is the lockup control solenoid. thats what engages the Torque convertor to lock up.

the linear solenoid is what regulates the pressure to change the gears and such I believe.

 

If it was a brand new transmission, it should have come with those solenoids. I assumed you purchased a rebuilt or remanufactured transmission, but the quality ones usually come with the solenoids also.

 

yeah it was a rebuild/remanufactured transmission but I did agree with them to use any electronic/computer from the old one as long it was in good working condition.
I had change the linear solenoid before rebuilding the transmission so I guess the top was going also soon or later. I am just glad for the warranty if not I would have to spend $200 more.
btw I hear ppl saying the dealer will just tell u to buy a new transmission if u get the code 0740 without even inspecting the tranny, thats weird.

 

sometimes not using honda ATF will throw the P0740 also.

 

I once use some other tranny fluid before the tranny went bad and I immediately notice the difference, the tranny shift more smooth using honda atf.
of course now I using Honda aft only.

 

That's because the checklist that applies to solving that problem on some models goes like this:
1) Check for missing or damaged o-ring on mainshaft (pull tranny)
2) Check solenoids with known good ones (some models require pulling tranny)
3) Some models recommend replacing torque converter with known good one (Pull tranny)
4) Some models recommend replacing PCM.
5) If all else fails, replace transmission.

The dealer doesn't like pulling the transmission multiple times so they quote the highest price option is see if the customer is willing to go from there.