Mercury Villager / Nissan Quest Automatic transmission TCM TCU ECU Up for sale is a Working, in excellent condition TCU. Nissan number-- ETC N40 / ETCN40 / 31036 0B000 / 310360B000. This unit offers a 30 day functionality warranty. This should fit many As always with this type of component your best bet is to match the part number to the one on your original TCU. A faulty TCU can cause all sorts of strange shifting issues with these transmissions. These can also cause issues with erroneous check gearbox lights. If your car does not have these issues but you intend to keep it a while, I recommend our customers keep an extra TCU in the trunk. These are generally fairly reliable units, however they can be damaged by faulty wiring or voltage spikes caused by a bad alternator. These units now have to be special ordered from most dealers new for big $$ (often times over $1000!), and you can never find one when you need one. Even now finding a good one second hand is getting to be quite difficult as these cars get older.