 Finding
the root of the problem
Electronic diagnostics play a vital role in modern car servicing and maintenance operations. Chris Graham discovers just how important experience and equipment is in the fight against the niggling fault.
One of the greatest and most significant revolutions to affect the modern
motor car came with the advent of electronic control systems. The mid-1980s saw an explosion of automotive technology and Mercedes-Benz, with close
development links to Bosch, was instrumental in much of the ground-breaking progress. Nowadays the most sophisticated Mercedes-Benz models would put
some of NASA’s earliest spacecraft to shame, in terms of pure processing power. The level of electronic technology involved is simply awe-inspiring. Today
computers control all of the most important functions on a car, from the running of the engine to the temperature of the driving compartment. Without
electronic control modules (ECMs) your car wouldn’t have state-of-the-art anti-lock brakes or traction control. The engine would be incapable of
meeting the latest exhaust emission control standards and you wouldn’t be able to enjoy the convenience of an automated service interval indicator. "Today,
computers control all of the most important functions on a car" The
adoption of fuel-injection heralded the demise of the carburettor and brought the internal combustion engine into a new age of efficiency. Now, the sky
is the limit in terms of electronic control. The modern engine and its ancillary systems bristle with electronic sensors designed to act as eyes
and ears for the main ECM. All are in constant communication with the cars central ‘brain’, relaying information about engine performance and the
driver’s motoring wishes. The ECM is pre-programmed with a complex set of operating parameters within which all
engine systems are designed to operate. If, for example, the Lambda sensor located in the exhaust
downpipe, detects an unexpected variation in the
exhaust gas quality, then an appropriate message is sent directly to the ECM. Comparisons are made with the stored data and, if necessary, action is taken
to correct the problem by adjusting the engine’s fuelling rate or ignition timing. These types of alteration are made many times a second, all the time
the engine is running, to ensure that the motor continues to perform at maximum efficiency, regardless of operating conditions. INTEGRATED
SYSTEMS
But the sophistication doesn’t end here. Engine management is linked to all the other electrical systems on the vehicle so that the gearbox, climate
control, security system and all safety-related functions remain effectively in step. Perhaps most impressive of all is the main ECM’s ability to
think around problems. As an engine ages its performance changes. Even with a mighty Mercedes-Benz motor, mechanical tolerances do begin to slip as levels
of wear increase, and this inevitably alters the way the unit runs. However, the car’s brain is designed to adapt to these minor deteriorations by
tweaking an output here and adjusting an input there. What’s more, if an important sensor happens to fail completely, the ECM
recognises this and sends the engine into what’s known as ‘limp home’ mode.
This allows it to continue running, albeit with reduced performance often combined with increased fuel consumption and exhaust emissions.
Self-preservation is the name of the game under these failure conditions, as far as the engine is concerned. It will do all it can to prevent unnecessary
damage, even to the point of shutting down altogether if there is a risk of serious mechanical harm being caused. "THE
CAR'S BRAIN IS DESIGNED TO ADAPT TO THESE MINOR DETERIORATIONS BY TWEAKING AN
OUTPUT HERE AND ADJUSTING AN INPUT THERE" Of course, the downside of this high-tech approach is a dramatic increase in
design complexity, which has knock-on effects on ultimate vehicle reliability as well as service and maintenance requirements. Motor cars provide a harsh
environment for sensitive electronics and faults are inevitable, even on a Mercedes-Benz.
At the heart of the problem is the fact that it takes very little to upset the status quo. Straightforward water or dirt ingress can be quite
sufficient to inhibit just one electrical contact which, in turn, throws the whole
system into operational disarray. It is the exploration, analysis and rectification of these often subtle faults which makes up the specialised
and exacting business known as electronic diagnostics. From the motorist’s point of view, the need for these problems to be dealt
with effectively is making it increasingly hard to opt out of the dealership network, should you wish to do so. Independent specialists who not only have
the necessary diagnostic equipment to deal with the latest vehicle management systems, but also know how to use it, are few and far between. One such expert with plenty of Mercedes-Benz experience is Simon Ashby, who
runs Reading-based Diagnostic Techniques (Tel: 07971 300481). He says: “The days of fixing cars with spanners and screwdrivers are long gone. It’s a
high-tech business nowadays, and being successful calls for levels of understanding and technical expertise which unfortunately leave many
independent traders floundering. In my opinion survival is all about investment in hardware, and the relative complexity of the latest generation
Mercedes-Benz models means that top quality diagnostic equipment is essential. Without it, the average technician has little hope of identifying
a problem, let alone being able to put it right.” Accurate fault identification is the key objective and achieving this
requires access to the management system’s fault code memory. All system failures are logged within the
ECM, as a simple code number which relates
specifically to the cause of the problem. Many manufacturers fit their vehicles with convenient fault warning lights on the dashboard, to alert the
driver when a problem has been detected, Unfortunately, German designers have been historically reluctant to include such helpful aids, presumably feeling
unwilling to admit to the possibility that something might actually go wrong. Therefore, on Mercedes-Benz most models, faults present themselves ‘out of
the blue’, once they have become bad enough to cause drivability problems or annoying MOT test failures. Simon adds: “For a long while technicians at the dealerships were the only
people who could get in to interrogate the fault code memories effectively, using the officially-supplied HHT tester, to identify fault causes.
Thankfully the position is different now and independent specialists have a choice of readily available diagnostic equipment that’ll do just as well as
the dealerships’ kit.” DOING IT FOR YOURSELF
One such example is Carsoft, a Belgian product aimed specifically at German marques and distributed in the UK by Maverick Technology. It’s a
PC/laptop-based system that can be used on post-1988 models with both analogue and the more modern digital management systems. The software is
completely menu driven which makes it easy and quick to use. It will access and reset all Mercedes-Benz fault codes, can activate and drive components,
has a limited live data stream capability, can be used for ECM identification and new key coding and will adjust and reset service intervals. The
manufacturers have also built in a useful troubleshooting feature which helps to explain common faults and provides tips on effective rectification. The
system is supplied with all diagnostic cables and is available for just under £1,500 (plus VAT). Simon has been using the Carsoft software for a while now and has been
genuinely impressed with its performance. He explains: “I’ve loaded the system on to my laptop which is really convenient for mobile work. The
program works reliably and, unlike many others of its type, never suffers from infuriating system crashes. The information provided is accurate and
the simple controls make for speedy, efficient diagnostics. My only gripe concerns the lengthy initial set-up procedure, which involves the inputting
of a horrible 32-digit code number! "INDEPENDENT
SPECIALISTS HAVE A CHOICE OF READILIY AVAILABLE DIAGNOSTIC EQUIPMENT THAT'LL DO
JUST AS WELL AS THE DEALERSHIP'S KIT" “The system works on all aspects of most Mercedes applications, including
the braking and traction set-ups on diesel models, and those which it does not cover are extremely rare so that’s not really a limiting factor in my
experience. The live data streaming feature is a useful one for monitoring the output from sensors as the engine runs and, although this is limited at
present, Maverick tells me that the function is being expanded as the software develops.” There is little doubt that products such as Carsoft will do much to loosen
the perceived maintenance stranglehold applied to many Mercedes owners by the dealerships. The sense of obligation you might feel about continuing to have
your newish E-Class ‘officially’ maintained need not be such a concern. Echoing the sentiments of Churchill's famous ‘Give us the tools...’ quote,
independent and experienced experts at last find themselves in a position to work successfully on the most complex of faults in complete confidence. Maverick Technology can be contacted on 01280 816333.
For more information e-mail info@www.mavericktechnology.co.uk
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