Volvo Repair: 2000 S70 SE - gearbox issue, automatic gearbox, speed signals

Question
While driving on the freeway today my "check engine" light came on along with a flashing Mode "W" engaged light (light is shaped like an arrow pointing up)When I look in the owners manual, it states that this means that there is a fault with the automatic gearbox. The car has about 120000 miles on it. The car seems to be driving OK, but I am worried about driving it. Before I take it to the shop I wanted your opinion and an estimate of the cost of the repair. Thanks for any advise you can give me.  

Answer
Sorry about that.  Don't know why it thinks i said outside my expertise.  There is a fault in the transmission and it could be any number of things.  It is impossible to tell what it is at this point but, its either gonna be fairly in expensive or REALLY expensive.  More often than the other its an internal failure and you will need a whole transmission.  You can still get lucky and get something unrelated to the transmission.  Communication errors with the transmission module will set the same kind of problem.  If your abs module has failed, it doesn't send vehicle speed signals to the transmission module, and the the transmission module will set a code.  So the things to look for are, an ABS module, a whole new transmission, or nothing at all if its something really simple.  Although that last option is the least unlikely.  An ABS module would probably run about 1500 dollars, while a transmission would be more like 4000 dollars.

James