Finally fixed that pesky Vectra diesel

"Mrcheerful" wrote in news:hlUtk.49689$ snipped-for-privacy@text.news.virginmedia.com:

Nicely done, but don't you think things are getting stupid these days with regards to diagnosis? ;-)

Sounds like reading the codes was pretty useful, it effectively diagnosed a vacuum problem which meant the OP knew where to look.

I might not have trusted some people not to have simply replaced the EGR valve and the turbo in the light of that evidence however.

It's a bit unuseful that the OPs main scanning tool didn't read the manufacturer's codes I suppose.

Really, if there was a general 'low vacuum' sensor then that would have been more useful. The part that had actually failed was not indicated by either of the codes. The most useful bit was actually typing the details into Google, which gave me the low vacuum lead, the actual useful diagnostic was the vacuum gauge, which by reducing the system to a minimum allowed me to find which component dragged it all down.

The code reader situation is going to remain a nuisance for a few years, as until 2004 they did not standardise codes across the board. The car is a 99 and my code reader is 2008 !! At least my reader could put the light out and cancel the codes.

The scanner that I used was about 2500 quids worth, not really worth it for me as a small garage, particularly since I can borrow it if needed !!

Mrcheerful

Tricky for the engine designer though, isn't it? If there was a general low vacuum sensor, it would add complexity and a possible unreliability to the system. I guess it would also make it more expensive for the manufacturer to produce which is probably the real reason it's not there. (c:

We had a problem recently where the intercooler on a TDI engine was leaking (

). There was a fairly generic sounding "boost control negative pressure deviation" error code stored. Googling told me to go looking for problems with the vacuum operated boost control gubbins as we never suspected it was as simple as a boost leak but at what point do you stop adding sensors to find out where the problem is? I'd have benefited that time from "wastegate actuator a bit gummed up", "wastegate control solenoid dicky", "low vacuum" and "intercooler damaged" sensors.

As a mechanic, do you think that modern engines are better with or without on-board diagnostics? I think it'd be way more time consuming diagnosing things without them, but that they aren't as clever as some people like to think.

Douglas Payne gurgled happily, sounding much like they were saying:

Diagnostics aren't _that_ recent an innovation, of course - the Lucas CU14 injection on the 18yo Saab allow fairly full fault codes, using only a wire with a switch in it, with codes read out by counting the flashes of the engine management warning light.

Some sort of fuzzy logic as to the cause of the code would be the best, or inbuilt Google !! Like I say, in my case a code to show low vacuum would have saved some head scratching, and I can't believe the extra cost of another sensor is really that high, in my case it would have saved much more than its cost in time, diesel, pollution, etc.

The initial fault that brought the car to me showed no fault codes of itself at all (the failed pump) Now that would have saved a little while if it could have said 'main injection pump failure' As it was expensive and a long job to change I did not want to replace it without being sure that it was really faulty.

A code showing 'low speed swirl valve operation fault' would have helped too. A sensor to check whether the valve actually moves would again be cheap enough. I reckon if you are going to do the job then there should be sensors for all likely failures, and why not have a little display on the car that tells you in English which sensor has triggered a fault.

Mrcheerful

I can't imagine a situation where a mainstream maker would add a sensor purely for diagnostics. It would need to earn its keep either by making it easier to comply with pollution regs, or by offering some sort of added value to the initial purchaser.

As most cars are effectively bought from new by accountants, telling them that a price increase is due to the vehicle being easier for the garage to diagnose faults isn't going to work!

I worked as an industrial electrical technician. Manufacturing machines are about 20 years in advance of cars WRT the levels of electronic technology they use.

I used to have steam coming out of my ears when asked by a mechanical tech or a manager "Can you just pop down and plug your magic box in to tell us what is wrong with this machine?"!

Chris