Diagnostics and repairs for Steering & Car Control can be challenging. Even with every test in Car Mechanic Simulator 2015 you likely won't find every defective part. This category of problem also overlaps quite a bit with Running Gear Problems.
Two tests that can really help you diagnose steering & car control problems in Car Mechanic Simulator 2015 include the Path Test (also called Test Path) and a simple Test Drive. Be careful with the Test Drive as the car will likely be very difficult to control. You can't actually damage it during the Test Drive, but you can frustrate yourself quite a bit if a 2 minute Test Drive turns into 20 minutes!
Also keep in mind that Running Gear Problems do overlap with this category quite a lot. The things to check first are the steering rack, front sway bar, and tie rod parts. Shocks, springs, suspension arms, and their related parts can also be part of the problem. The same goes for the rear suspension.
Harder to find parts include the different rubber bushings, wheel hubs, and some rear drive axles. You'll want to make sure you don't over look these. All cars have 4 rubber bushings up front and between 2 and 8 in the back.
These can be hidden in leaf springs, axle knuckles, control arms, and the various suspension crossmembers. The more complex rear ends also have quite a few sway parts that can be difficult to see.
These repair orders show which parts were part of the problem. Keep in mind that this can be random, and some of these parts can appear in different or multiple categories. On the up side, these examples will give you a good idea of the things to look for when hunting for faulty parts.
To help you learn the diagnostics side of Car Mechanic Simulator 2015 as quickly and easily as possible, I have created a few short but comprehensive guides covering each problem category. For a complete listing of these guides, check here:
Diagnostics & Repairs - Car Mechanic Simulator 2015
If you are looking to learn about the early and mid-stages of the game, you may find these pages of interest:
Your Garage, Tools, Tests, & Upgrades, Jobs & Job Management
And if you are wonding what awaits beyond and where the real cash is hiding, check out this link:
Rebuilding Guide - Car Mechanic Simulator 2015