Seems like a huge coincidence it stopped working at the same time it was visiting the dealership. I suggest you take it back and complain that they broke your seat.
You have nothing to lose and will probably get the fault diagnosed free and maybe more...
Engine sensor , ignition control sensor ! Is the vehicle check engine light on ? Do you have a scan tool to check engine sensor data ? Do you have a DVOM - digital volt ohm meter ? any sensor that is powered by the PCM - engine computers five volt reference voltage circuit . 5 volt reference or crankshaft postion sensor . Doing testing is the way to find the problem .Check out videos on ignition system testing .
You will need the key to unlock the steering so that you can remove the ignition housing. This is done as an anti theft measure. The only other way is to get a locksmith to unlock it for you, or break it.
If an auto tranny there should be a dip stick.
If a manual tranny, there's a fill bolt near the top of the tranny, you have to :feel inside to check oil level.
I usually fill it till it starts to spill out oil, then recap and tighten the bolt.
Well code 171 is telling you the fuel mixture is too lean for bank one and code 174 is too lean bank two.
So the most common cause is low fuel pressure.