In one swoop technology has made generations of experience obsolete. A car which twenty years ago misfired -   check the points, distributor cap for track marks, plug leads for shorting, no they’re okay. Look down the carb, spitting back? Yep, burnt valve. Head off, decoke, grind new valve in (replace them all and the valve guides if you can afford it) and Bob’s your uncle.

That was just an example, we can all list many more. If a car misfires now – check the plug lead and the plugs – and that’s it. Take it to the Main Dealer and you’d better have deep pockets.

Some faults will always be easy to diagnose: if there is oil dripping from the engine, the mechanic will hoist the car and peer about with a torch until he finds the wet patch. If the leak is not obvious, he may clean the engine and then take the car for a spin and have another look: the leak will now be apparent.

But it is the electro-mechanical faults which can defy diagnosis. Intermittent faults are the worst – but they always have been. Even a main dealer was reduced to guessing which item was causing the problem and used trial and error to substitute a part and hoped that worked.   A mechanic scratching his head and making a hissing noise through his teeth was just the same in 1920 as he was in 1990.

But computer chips have proliferated in automotive systems, so that they now control everything from engine management, locking, alarms, instrumentation, automatic gearboxes, brakes, traction control, climate control and even seat position. And a computer chip can communicate with another computer chip …

WDS2000 is Fords latest World Diagnostic System released in 1996 for all OBD2 equipped vehicles. It replaced the earlier FDS2000. It is a lap-top computer which receives a diagnostic routine from a docking station and is then carried to the Ford model and plugged into the diagnostic interface. In the Scorpio this interface is concealed on the top of the change cubby to the right of the steering wheel (RHD vehicles). This serial interface connects with the engine management system.

The operator follows the program on the laptop by using the touch screen, following a set routine while the WDS communicates with the various modules which may be affected. At the end of the routine the operator is informed which part or module is faulty and needs to be changed, or is told the next program to download to continue the diagnosis.   By following the instructions on the screen, touching the screen to confirm each stage and move on to the next, the operator ends up with the solution, and is told the action to take.

But supposing the fault only occurs at seventy miles an hour? Well, no problem. The WDS can be used by a skilled and trained operator for running tests so that it can look for the fault while the vehicle is being driven. This option is called the Datalogger, but it needs a skilled operator who is experienced in operating parameters.

Most of the modules used in the Scorpio, like the EEC V engine management and the PATS system, store fault codes in memory for ten cycles (ie, individual uses of the car) and WDS can pick this up in seconds. This code then enables the unit to branch to a specific routine which will then make further tests until the exact problem is identified. It can also be used to upgrade the engine management system with revised engine timings introduced as the result of problems discovered elsewhere. (The EECV PCM can be completely wiped and reprogrammed from scratch.) Even the diagnostic routines themselves are updated regularly, which takes full advantage of the experience of other operators anywhere in the world.

So if in the future you take your Scorpio into a main dealer and complain about a problem with the transmission which only occurs after ten minutes at 46mph, you’ll know that they have the ability to fix it. They might not have a man skilled enough to use Datalogger, but they should find one. If they make excuses – don’t have a rolling road – can’t do diagnostics on them, they’re too new (or too old) - they don’t have the right interface - can’t store the results – there’s no n in this month - and all the other old tosh they come out with, you’ll be able to look them straight in the eye and say – “Put it on the WDS while I drive it and let me see the results on the screen.”