Edited to separate the relevant parts. Hope you don't mind Flavio.
Second, thanks to modern engine control units, just plug a scanner that "talks" to the ECU and it will report you immediately what is wrong with the engine. So diagnostics is easier.
It will only tell what its sensors "see". Whether the defect is mechanical, electrical, electronic or software related (or a combination of these) is still up to the person in charge of the repair. The self diagnosis could even be the culprit.
Case in point from my father's car: Speedometer suddenly gave up the ghost. in this car, it is electronic, and coupled to a sensor in the gearbox. No problemo, buy a new one and install it. Literally 5 blocks away after the repair, there it goes again. Back to the shop, guy replaces it AGAIN... 5 blocks and... you guessed it. Father takes the car to another mechanic after getting his cash back. Turns out, the self diagnosis system of the car didn't "accept" the new part and somehow was burning it out. The fix? install a new one, and let the car idle till the auxiliary radiator fan came up. Really. When that fan comes up, a self diagnose cycle is completed, and "accepted" the new speedometer.
Third, instead of removing the carburetor for cleaning, you remove the injectors for service or replacement.
From my father's car as well, which is fuel injected. It is from 1997, and there are no new injectors available, either OEM or aftermarket. The injection module needs a specific nozzle shape to work, so when the injectors go, the engine will go too, since installing an aftermarket injection system is too expensive. Actually the whole car goes since putting other engine in would cost more than the car is worth. Expendability at its best. Same applies to some cameras manufactured too long ago to have spare parts available in abundant quantities, and which are no longer supported by its manufacturer.
Car maintenance has not become impossible at all, just different. I contend that (a) it is easier now, and (b) thus, modern mechanics know even LESS than older mechanics.
And isn't that more dangerous? We risk a generation of part exchangers instead of mechanics, when something breaks, replace it. Without further thought to the potential underlying cause. Like on my father's car speedometer case above.
Moreover, for those who think that electronic spare parts can't be manufactured... Nowadays you can replace, if you want, your engine control unit (ECU) with a do-it-yourself ECU, for example the "MegaSquirt" ECU. You build the hardware, the software is already made, then you configure it according to your engine.
FAR easier than having to design a the "ideal-for-your-engine" carburetor from scratch and then having to manufacture it, not to mention test it...
The devil's in the details, as they say. Not every engine will accept conversion to a MegaSquirt or FuelTech module well. And the configuration, the "mapping" of the engine is very tricky on some engines, too. Not to mention you may need some rather specialty equipment to get it right. It's easier than building a carburetor from scratch, but that's not what people do. They go to Edelbrock or Holley or such and get a carb that has the right CFM for their engine, and mount it on. Sure, they may need to adapt the fixation points, but you too have to do such things for the injection modules. Engine injection is more efficient though, no question about it.
If you had a "conventional" car with no computers, and your battery light turned on from time to time, you would have to review items 1,2,3, and 5 anyways. So there is no difference compared to "conventional" cars.
Except there would be less suspects. Believing the electronic sensors/modules/etc won't ever fail is a bit of a naivety. Another case, fresh from last road trip, same car as the speedometer problem:
Suddenly, I look to the car's temp gauge and it is off scale! (I'm sitting shotgun) I warn my father to pull the feck up, and turn the engine off. We lift the hood, the engine is very clearly overheated. I reach to the bottom water hose coming off the radiator and squeeze it, since I see no waterline at the reservoir. The damn thing is dry as bone! No water left at all. What the hell happened here??!
We let the car cool on its own. We had fresh water for the trip, so we fill the reservoir to the brim when the engine was cool. I close it, and squeeze the same hose again. A leak from one of the top hoses shows up, pretty big actually. It connects to the exit of the water pump, so most of the water being sent off the pump, leaks away. We do a stopgap repair, and complete the trip to the nearest mechanic. Turns out the hose was only partly the culprit.... One of the temperature sensors in the engine, the one that controls a valve letting more or less water flow through the block, went crazy, and shut the valve. The water loop was thus interrupted, and the water temperature rose to the point it weakened the rubber in that hose, and the added pressure of water vapor teared a hole on it. So what really caused this, was a freaking sensor. Again.
Ignition timing is nowadays controlled by the ECU. As long as the crankshaft position sensor works, timing will never go off. Compare this with the old schema of having vacuum controlled timing retard/advance (anyone who has worked with engine vacuum diagrams knows how this is a pain to service if there is a leak or if some component has aged), and centrifugally-controlled timing advance.
My engine (Mercedes M112 V6) has 6 cylinders but 12 spark plugs. And 6 ignition coils. If this arrangement used the 1970s distributor-ignition, plus the old big ignition coils, it would have taken LOTS of space under the bonnet and would have a maze of wiring to connect. Rather, the coils are driven by the ECU, no distributor. As long as the wiring is good and the spark plugs are good (and these are spark plugs rated to last like 100K kilometers), it should work just fine.
There's a little bit of oversimplifying the issue here Flavio, don't you think?
To sum it up, and to make an analogy to cameras. Electronics have been operating miracles, making stuff as precise and accurate and awesome as it has never been before. But there is an added risk of the electronics themselves betraying us. It is much a curse as it is a blessing. The rule of thumb is the simpler the thing is the less things it has to fail, and will always be.
And to address the "anti-electronics bias", I would agree were it not for the continuing miniaturization of components(solder a SMD with a loupe by hand anyone?), not to say of increased use of IC's which may or may not be proprietary, and may or may not contain proprietary firmware. If an electronic camera was built solely with discrete components, resistors, capacitors, etc and a few simple easy to find IC's that require no proprietary firmware, I'd be 100% with you Flavio.