So I have a 2002 Volvo S80 t6 and I'm having transmission issues. When I first got the car the gears started slipping a little a few months after I purchased it. One day after getting fuel I started the car and started to drive and made it 20ft. Before the car stopped driving, if was like every gear was nuetral. So I did some research and decided to change the filter and the fluid. After completing that the car drove again and I had no issues until a few months later. No the car drives but the only gear that I can drive in is manual 3rd gear. The car has 189,000 miles on it. It also has the transmission service urgent message showing. I was wondering if anyone has any advice on what I should do? I really love the car and the motor is still strong. I need some advice. Thanks in advance

 

start by reading the transmission fault codes via an OBD2 code reader. Generally transmissions can have issues 1 of 3 ways: 1) the wiring/connections between the ECU, TCU (transmission computer) and the transmission are not getting the correct signal to the shift solenoids 2) the shift solenoids or related valve body are not actuating properly 3) the clutch pack is worn and unable to effectively transfer power. The fault codes will tell you things like whether the expected voltages from the solenoids are being found, if the transmission is overheating, if its slipping (ie road speed doesn't match engine speed for a given gear selection) and so on. Until you get some more data, you don't know if you need to clean up the wiring connectors, replace a solenoid or valve body (which can be done with the transmission in place or you need to replace or rebuild the transmission. You can do some research on finding a used replacement via car-part.com just to price the market.

 

So I used an ob2 reader and found these codes:
P0700- transmission control system (mil request)
P0751- shift solenoid "A" performance or stuck off
P0756- shift solenoid "B" performance or stuck off

I'm not sure exactly what I should do

 

P0700 is saying the TCU detected a fault and the other two explain what was detected. This can be either a wiring issue or you need to replace the shift solenoids (or valve body). Unless you plan on opening the transmission on your own, you can start by cleaning the connectors to the TCU and transmission, inspect the wire harness etc. After that you'd probably want to search youtube for some vids on replacing solenoids/servicing the valve body to see if you want to do that or send out to a pro.