E240 Year 2000 problem with gear box

The electrical connector "o" rings leak on the 722.6 transmissions and there is an updated "o" ring. If you remove the connector by sliding the lock upwards there is a 7mm. bolt holding the housing onto the vavle body plate located in the center of the pin connector on trans. Remove that 7mm. and pull housing out of trans. there are 2 "o" rings on the pin connecter and one on the harness connector. M.B. sells the 2 for the pin connector and the harness connector comes with the hole connector but you have to remove all the pins out of the old one. The harness connector is not the problem just replace the 2 on the transmission pin connector. Make sure you add M.B. electrohydraulic trans. fluid to the transmission. You will have to purchase a dipstick from the dealer because there is onlya housing tube. The trans has a red color lock and the oil a black color lock. They are right next to each other so be careful not to confuse the 2. I have seen them leak bad enough to fill the trans computer full of oil- The E.T.C. module is located in the r.f. foot well in the false floor under carpet. I do not know what circuit board you are refering to. I'm assuming it is the valvebody solonoid plate. After repair I would recommend having the car scanned and cleared for codes assuming the module is not full of a.t.f.. You may be able to clear the codes by disconnecting battery neg. for at least an hour to drain capacitors but it is always best to have car scanned. Good luck