2003 Honda Odyssey, 64,000 Miles. Always TCS and engine light come on at the same time. Used Actron auto scanner 9180 and found code PO740 TCC CKT malfunction. History-I noticed trans. leak 2 years ago. My mechanic changed the trans. oil at the time, but the leak continued. For the past few months I have noticed that when the RPM goes up(specially in 1st gear), the car is low to respond. The oil dark in color. I have read many contradictory articles and opinions as to what to do next. Example. Change oil or not. Flush oil or not. I would like to hear from all smart/wise mechanics out there as to what I should do and why. Thanks.

I have a 2002 Odyssey that has had transmissions problems. My research led me to flush the transmission fluid by changing it 3 times in row with just a few miles in between. (each change only releases 3.5 qts. and the transmission holds 8). This way you get 90% of the old "worn" fluid out and replace it with new fluid. Use genuine Honda ATF. The problem is that Honda fluid has special friction modifiers in it that eventually lose their effectiveness.

For a good take on this go to the Lube Guard website and read about friction modifiers. You can boost the friction modifiers in your current fluid with a Lube Guard product (or others) but remember that your current fluid may have been overheated and may also have contaminates from clutch discs that are wearing down.

The ATF is easy to drain, not so easy to refill. The drain plug has a large magnet on it to catch metal particles and shavings. This is a good indicator of the amount of damage that has been done. When you remove it, take a picture of it so you can show it to a transmission shop if you ever need work to be done at a later date. The refill plug on the top of the transmission may have been modified with a factory replacement part (part of a recall) that takes fluid from a splice in the transmission cooler line to a fill plug with a nozzle in it. The modified fill plug squirts some cooled fluid onto the second gear. So the new fill plug has a fluid line going into it. It can still be removed easy enough but you will need a long narrow funnel to pour new fluid in.