New engines aren't that much of a mystery. The basics still apply. It needs spark, it needs fuel. In the days before computer, the human computer set the spark in relation to the piston position. The human computer determined how much fuel to add to the carburetor and determined if it was too rich by smelling what comes out of the tail pipe.
These days, a computer adjusts everything. So, we have sensors and switches to tell the computer when to spark or add fuel. Break it down by systems. In the fuel system, the computer wants to know the air temp, air flow OR absolute pressure. Did somebody step on the pedal (throttle position) to add air and change the sensor readings. Then there is the spark system. What position is the crank in. Maybe even in relation to the camshaft. Is it the optimal time to trigger spark? Back to the fuel system, after the combustion, does the exhaust show the right amount of burn? O2 sensor. If not, should it richen it up or lean it out?
You might need a few newer tools to diagnose this new stuff. But it still pretty basic. You can probably diagnose and fix most stuff with a DVOM, test light and your ear. Or, you can get a somewhat fancy scanner to see what the computer sees. As long as you know what you should see and the computer is seeing the same thing.
Which is usually how you pass the ASE L1 test. Knowing that the GM system is based on a 5v reference and what most of the sensors do.
