Yes, there is certainly a need for skilled mechanics, you cannot use a computer to diagnose a bent tie-rod or a piston with worn journal bearings, it takes experience and a good ear. The problem is that a lot of issues that a mechanic could resolve in the olden days using a timing light and a screwdriver simply can no longer be resolved that way. Modern cars have electronically controlled fuel injection systems which include mass flow sensors, knock sensors and sensors within the catalytic convertors. The electronics have rom maps that are used to determine optimum fuel flow rates given all those parameters. There is simply no way to work out what is going wrong with such a system unless you are able to monitor the sensors in real time. Timing is no longer set by twisting the distributor because cars don't have distributors any more. The ignition module uses a sensor to determine at what angle the crankshaft is and then pulses individual coils. You see, its these kind of issues that make it practically impossible for a traditional mechanic to work on modern cars without appropriate diagnostic tools. Take an auto-electrician for example: There was a time when each button switched power directly through itself (like the window up down button) this is also hardly ever the case these days. The window buttons on the drivers side, you know, the four or 5 buttons that are sometimes placed there for remote control, simply have 4 low power wires connected to the module 0V +12V CAN-H & CAN-L. So the traditional auto electrician is unable to repair a faulty window problem unless he can easily fault find using the diagnostic tools. That is why so many components are just swopped out, people keep swopping bits until the problem goes away.
After market diagnostic tools have been around for years. Bosch makes a range of tools and so do many others. There is a company in Cape Town that supplies an amazing tool for VW called VAG-COM. It is a module that plugs into a laptop with a bit of clever software. The problem with the diagnostic tools is that each manufacturer makes lots of function proprietary and they also change them all the time. You not only have to know what the error codes are, you also need to know what it means for a specific year model. The way after market suppliers figure this out is by tapping the diagnostic bus of a OEM tool on the particular make and model. Then it is a long slog to work out the unknown commands and codes. Manufacturers are very clever, they run various protocols at various bus speeds just to confuse the issue. There are cars today that have surpassed CAN-BUS and now use fibre optic MOST-BUS. The reason being that cars need high speed communications throughout their various control systems.
An interesting signal is called the "crash signal". Cars fitted with airbags have a sensor fitted in the lower middle of the car. The sensor is really a 3 axis accelerometer. (Some cars are also fitted with yaw and roll sensors) This is how the appropriate airbags are told to inflate. Cars can even determine whether they are going into a roll by interpolating the lateral and horizontal acceleration information (That is how a drop top Merc 500SL knows to pop the roll bar up before the car is actually upside down) Anyhow, when the car detect a sudden deceleration the crash signal is sent across its main control bus causing lots of things to happen at once; on really upmarket cars it is like a fast action shutdown; seat belt tensioners fire, head restraints position themselves correctly, the steering wheel is withdrawn, the motor is turned off, fuel supply is shut off, doors are unlocked, appropriate airbags are deployed and on some cars even the radio is turned off and the hazard lights turned on. Although I often rant about the price of cars, the technology within them is absolutely astounding.
There will always be a need for a guy holding a spanner in the one hand, the only difference is that he now holds a sophisticated and very expensive diagnostic tool in the other.
The term "diagnostic tool" is not totally correct - the same tool is also used to change setting within the cars electronics - one should really refer to it as a diagnostic/adjustment tool
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