the speedometer doesn't work, the cruise doesn't work,

My first guess is VSS. vehicle speed sensor located on transmission yoke

 

A temporary solution is to stop for a minute, turn off the truck for a few seconds and start it back up. Everything should start working again. Drove an 09 volvo for 3 years and had this happen twice and that worked for me.

 

It either two things, VSS or the Accelerator Pedal Position Sensor (which is located on the Accelerator Pedal) or the Pedal itself. The Solution is to replace Vehicle Speed Sensor and replace the Accelerator Pedal which over time gets play in it and doesn't always read back to Zero right away which affects the signal to the ECM causing the Cruise and Engine Brake to disengage and act erratically.

 

The easiest/cheapest way is to get diagnostics ran then do the repairs yourself if you chose. That's if you are an OO. Otherwise companies pay for repairs find a shop. The mechanic can tell you in just a minute what's wrong after he hooks the laptop up.

I know if you unplug the VSS the truck will run like total crap so I tend to think it might be something else like the instrument panel itself since the speedometer doesn't work. All that stuff is integrated with the ECM. Not only could it be a bad device it could be wiring or a bad connector. Buying parts and guessing usually costs more.

 

CondoCruiser nailed it. Diagnose before you start throwing parts at it. I've never used Volvo software, but they all pretty much do the same thing (even if they don't all take the simplest path to get there). You make sure the voltage to your speed sensor is correct. Then you check the position reading on the clutch and accelerator pedal pedals when they're not engaged.
Another way to figure out your exact situation, if ever you end up with a DPF equipped truck (which your 07 won't be), is that the truck will still regen with the speed sensor disconnected (sometimes, you even have to disconnect it to regen, because the vibration can cause the ECM to think the truck is in motion, and it'll shut down the regen), but won't if the sensors on the clutch or pedal read that it's in any position other than the neutral position.

 

Good deal! Did you take it to the dealer and pay hundreds of dollars in excess labor/diagnostic costs like was suggested or did you do it yourself?

 

why not to pull all VECU fault codes first and post code list here?