AudiForums.com - Unknow Issue.

I have the following issue with my Audi A4 B8.5 2012 2.0 TDI Quattro 177 HP :

"Steering Lock : Contact Workshop" : It randomly appeared on the dash after washing the car, it stayed on for a day, then dissapeared for more than a month , now it came back again with more serious problems being:

When I put the key in the slot , I push it with my foot being off the clutch , the car gives "Steering Lock : Contact Workshop" fault. If I press the clutch and push the key once more, the car does not even want to crank, just takes off the ignition. If I push the key in several times, sometimes after 10-15 tries the car randomly starts, but still leaving the "Steering Lock : Contact Workshop" fault on the dash.

The Start - Stop System works fine, if the system stops the car at a red light, when I put my foot on the clutch it starts the engine without any problems.

I found out, that my car has a battery installed, which is not for cars with start - stop system. I also learned that on the minus side it has a sensor, which could be faulty because of this battery? Does it worth changing it , or trying to change it?

VCDS software showed a malfunction at terminal 15 , "something something short to minus (or plus)". Unfortunately I don't have an OBD scanner, neither the VCDS software, so I don't have the scan, also I don't exactly remember the fault it showed on the scan.

I don't want to take it to a mechanic , because I fear that it will be really expensive, since they did not even know what the issue was.

Does anyone has an idea what could cause this type of fault?