That's OK - a TIP122 is a darlington transistor (two transistors in the one plastic package) it might still have a driver transistor connected to its base.

I would strongly suspect the TIP122 is shorted and so taking the coils connection to ground permanently instead of switching it on and off as required.

This transistor is supposed to simply act like a relay but if it is shorted the coil will remain activated.

In the swt book a Q17 (Part No: 110-0067-00) is called a TIP122

Sorry I'm learning here