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Originally Posted by Oldandslow
Many thanks to everyone for their comments. I too have suffered the same problem, however, once the Brake Position Sensor (£278) had been replaced another fault was discovered, this time the Brake Pressure Sensor with a price tag of £1285. Volvo have offered 40% as my S40 is 6 months out of warranty. I have recently retired from the aircraft industry where data bus fault reporting is a similar and very difficult art. I am now trying to convince the local garrage to examine and think about the problem before they change another box.
Lets not beat about the bush, it takes a clever systems engineer to decypher some of the information and I feel the motor industry is not generally equiped to handle the situation. There are 2 ways of dealing with it, you either train your engineers or write sophisticated software to solve the problem. None of it easy and none of it cheap.
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Quote:
Originally Posted by 7050man
This is a fair comment. The problem is that the average dealer will not have anyone with the experience or time to take on an intermittant fault.
On modern auto motive systems like this, a slight voltage fluctuation, electrical noise or an irregular cpu input signal , can either generate a false code or genuine code that may not return.
The other common misunderstanding is that the computer is king. This is a myth. The computer may well give a clue as to where to look and in the case of a solid fault, will take the technician to the relevant faulty sensor. However with an intermittant fault, it only assist in gathering data. It's then down to the person who understands the car electro mechanical system to decide how to use the data.
This is where eyes,ears brain and possibly a good wiring diagram come into it and the time to investigate.
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And this is the infuriating situation in which I find myself.
I have little to no understanding of mechanics and absolutely none about electronics and computers, and this is why I pay main dealer rates to have these issues investigated. I'm a numpty and these guys are supposed to be the experts.
My concern is that the master tech seems to be of the opinion that at least some of these fault codes are genuine and is trying to pin down precisely which system(s) is faulty without considering that it might be the ECU itself that to blame. From my position of total ignorance I would have imagined that such as cascade of fault messages (some of them quite major) should be signalling that the fault could be elsewhere other than in the systems flagged up, as with Wheelie's alternator.
I would have hoped a trained tech would be asking more questions and carrying out more investigations to determine the true nature of the fault. By all means hook it up to the diagnostic machine, but if the data received as a result is baffling and if the owner's experience of the car if at variance with what would be expected in the light of the data on the diagnostics, then perhaps this is the time to question the reliability of the data and to consider what else might be wrong.
But then perhaps in my ignorance I'm missing something really simple. Wouldn't it be great if we had our own tame Volvo tech on the forum to illuminate areas such as this.
On that note, apart from duff batteries and alternators, are there any other external systems that could play merry havoc with the ECU in this way?