I know it is a loosing proposition but I still try to do some of the work on my car myself.  I do not have the fancy computer that plugs in under the dash to run a quick diagnostic check of all the systems to tell me which black box needs to be repaired next.   I do have access to the auto repair manuals so can find out the step by step procedures once I have figured out what the problem is.  I have really hated to see us transit from repairing worn parts to replacing black boxes that fail to function causing the system to shut down.