I have a passat 2005 2l tdi it always telling me engine fault go to garage.....why that happening.

https://www.google.com/search?q=Engine+diagram+92+geo+storm+gsi&biw=1362&bih=650&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjYzZrkhpjQAhWBfCYKHd5eCVMQsAQIGg#tbm=isch&q=Fault+code+16618+overboost+Passat+2.0+tdi+estate+sport+2006+is+ther+anything+I+could+test
Hope this helps

P1040 VOLKSWAGEN - Injector 1 Supply Voltage Circuit Malfunction

Symptoms:
- Engine Light ON (or Service Engine Soon Warning Light)

Possible causes:
- Injector 1 circuit open or shorted
- Injector 1 circuit poor electrical connection
- Faulty injector 1

Test it and keep us updated.

Exhaust pressure sensor a possibility if it has a DPF (diesel particulate filter). Has it had its fuel pump recall, the oil pressure light could be just the constant cranking and running the battery low.

HI
Think you have problem with Unit-injector. if one of four is damaged, car will not start. Tester will tell you wich one is too blame. If this is the case, change the instalation under cilinder head cover too (necessarly).
Marko

some lose connection at dashboard instrument cluster -ve earthing point is lose, so it is happening , or any socket is lose.

this could be due to a large variety of possible different faults, the only way to tell is to take to a garage for it to be plugged in to a diagnostic code reader. Not always serious, somtimes as simple as an engine coolant temperature sensor fault, cheap to buy and quick to replace.

If light is on at start up its usually a glow plug gone .Won't make any differance to driving. You should get a diagnostic scan done which will tell you which plug is at fault.

Air mass sensor, almost never shows codes but always makes the vehicle loose power !! cheaper from vw than pattern and more reliable

Hello, this is a common Fault with the bora/ Passat/ Golf. It generally tends to happen once your car has done 70K plus.
It's more of a electronic fault than an actual physical fault with the turbo.
What happens is when you are accelerating/ or applying an additional load to the engine, like going up a hill for example,the the turbo boost sensor tells the engine management system that it's over boosting (supplying the engine with too much boost pressure or air) the engine then goes into self preservation mode and will not allow the turbo to boost anymore and therefore does not allow your car to accelerate any more than it had been doing prior to the issue. A road side fix for this is to switch your engine off for a minute let the sensors re-set themselves and he presto the problem goes away.
You can be one of the lucky ones that this only happens to a few times, so some other people seem to have a re-occouring problem with.
It happen me in my 2001 Bora on the way back to the UK from a holiday in Germany, not very plesent when your in the overtaking lane doing 100mph+ on the Autobahn ;-).
After switching the engine on and off numerous time through Germant and France i finally got back to the UK, and brought it to my local Garage, who hooked it up to a Diagnostic machine, cleared the engine faults and i've not had a re-occurance since.........
Hope this helps

As a general rule with a modern VW TDI, if it isn't running properly go and get the engine fault codes read by a properly equipped garage. If your usual garage doesn't have the correct equipment I'd recommend finding one that does.

There are so many things that could be wrong that guessing is usually a waste of time, so "get the codes read" :-)

My '96 Passat TD (not a TDI) overheated last week and the battery light came on - it was a failed alternator belt which drives both the alternator and the water pump.

Hope this helps, D.