1.2 TDi speed sensor shenanigans

WallK

WallK

Member
Hello! I'm having trouble with my gearbox speed sensor (or other ones that work in tandem with it)
My speedometer works intermittently, I think tight turns and potholes are triggering its weird behavior sometimes. Also, it usually dies after a bit of driving when it's hot outside
Now my throttle pedal becomes unresponsive sometimes (just as RAB said it would), gearbox stays in gear though. If I put in in neutral -- I can rev the engine just fine, but it doesn't want to drive.
Speedo comes back to life if I keep RPMs high (this is how I got the car home after the last fault, kept it in a gear one lower than needed and tried to keep gas pedal pressed all the time) but will drop to zero if throttle pedal is released or revs go down after a shift.
Sometimes everything is ok for 200km at a time, sometimes dying speedo doesn't affect throttle pedal (it does affect automatic gear shifting, but it is manageable)

I have changed gearbox speed sensor twice (just to be sure, but I think my original works just fine, it's resistance measuring 0.8KOhm, that's a normal reading per manual)
I've changed connector and redone part of the wiring that comes to it, all to no avail

This thing started happening after hydraulic gear changer rebuild and clutch cylinder swap to a Hall sensor one. It wasn't done by me, gearbox works fine as does the robot (maybe a bit leaky still, but much better than it was before, constantly losing gears and stuff like this)

What else should I look at? Could something else be damaged by hydraulic robot repairs?
Thanks!
 
It could be that the clearance between the sensor and the output shaft is getting to the point that it is excessive. In the early days of the DSK (and maybe FLE), Audi/VW had a problem with excessive preload on the output shaft bearings which causes them to degrade. I have had this same problem with our 1999 Lupo 3L. That it happened after other transmission work is most likely coincidental. To be certain, you need a full diagnostic scan.

RAB
 
RAB said:
It could be that the clearance between the sensor and the output shaft is getting to the point that it is excessive. In the early days of the DSK (and maybe FLE), Audi/VW had a problem with excessive preload on the output shaft bearings which causes them to degrade. I have had this same problem with our 1999 Lupo 3L. That it happened after other transmission work is most likely coincidental. To be certain, you need a full diagnostic scan.

RAB
Click to expand...
I have a scan ready, but it was done by a friend with a fake VCDS, so it's in russian
But maybe you can recognize error codes

Code: 
Адрес 02:  Электроника коробки передач        Файл QML: 6N0-927-735.clb
   Номер детали: 6N0 927 735 D
   Компонент: DS085 Getriebe      3081
   Кодировка: 00000
   Мастерская #: WSC 00000
 

3 Найдены неисправности:
00263 - Коробка передач
            27-10 - Недостоверный сигнал - Непостоянно
00845 - Датчик распознавания селектора АКП в положении N(F258)
            35-10 - - - Непостоянно
00625 - Сигнал скорости
            27-10 - Недостоверный сигнал - Непостоянно

It doesn't make a lot of sense in russian, but it's basically like this:
Code: 
00263 - Transmission
            27-10 - Implausible Signal - Intermittent
00845 - Gear selector sensor in position N(F258)
            35-10 - - - intermittent
00625 - Speed signal
            27-10 - Implausible Signal - Intermittent

First fault usually meant that I need to go through adaptation, but it could be something else now
 
Last edited:
The good news is that it's probably not your gearbox at fault. When my gearbox failed, the error codes were 00263, 01612, 00297 and 00841. 00263 can be caused by simply disconnecting the hydraulic unit. You might have some poor connection issues and one of the sensors on the gear selector might have failed.

RAB
 
RAB said:
The good news is that it's probably not your gearbox at fault. When my gearbox failed, the error codes were 00263, 01612, 00297 and 00841. 00263 can be caused by simply disconnecting the hydraulic unit. You might have some poor connection issues and one of the sensors on the gear selector might have failed.

RAB
Click to expand...
Great to hear, thank you!
When I had errors checked before (when speedometer just started acting up and I've changed the speed sensor) -- I had only the 00625 error
I'll look on gear selector sensors, but I'm not sure it will do anything about speedometer issue

After clearing all the errors and driving for a bit I've got the car rescanned and only climate module errors (that were always there) remained
 
RAB said:
The good news is that it's probably not your gearbox at fault. When my gearbox failed, the error codes were 00263, 01612, 00297 and 00841. 00263 can be caused by simply disconnecting the hydraulic unit. You might have some poor connection issues and one of the sensors on the gear selector might have failed.

RAB
Click to expand...
I think it happens when it's hot outside
Had some cold days and drove for a while without problems
Today's sunny and wife had throttle pedal to give up in less than 100 meters
 
Can anyone suggest what is my next move? It's not reliable enough right now to drive and it's my only car
 
You need to do a scan with VCDS. Then delete any faults and scan again.

RAB
 
All faults shown are not necessarily current. You may have a wiring problem somewhere. Any others apart from the three shown above? You should just ignore any intermittent A/C faults.

RAB
 
RAB said:
All faults shown are not necessarily current. You may have a wiring problem somewhere. Any others apart from the three shown above? You should just ignore any intermittent A/C faults.

RAB
Click to expand...
No, nothing else
I'll try to make some more scans, clearing, driving a bit and scanning again
It's just not that easy to do right now
 
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