speedometer problems

[pete.y]

hi I have a 2000 c200 2.0 auto and in the last week I have had the problem that as I'm driving the speedo suddenly drops and the engine wont change gear so I have to stop and restart the car but this doesn't last long. I went on a 4 mile drive to town and back and had to restart it about 5 times this morning so it seems to be getting worse pretty quick! any ideas please

 

[grahamcol]

I guess some speed sensor or other has gone down and this (obviously) causes the speedo not to work and must also affect the autobox which, I presume, will not know the speed at which to shift gears.
Others will know better than me. Otherwise a Star test should immediately pinpoint the cause.
Good luck.

 

[pete.y]

where would I find the speed sensor please?

 

[grahamcol]

Not certain at present. I've a feeling it may be connected with ABS etc., but I could be wrong.
Others more knowledgeable should be along shortly.

 

[television]

Brake lamp switch maybe, but normally get message in Dash say no ESP/BAS

 

[pete.y]

I don't have any esp notifications on dash although abs and coolant low lights are lit all the time?

 

[television]

ABS light means a wheel sensor more than likely failed, and no speed signal. it really needs a STAR read out to make things easy.

 

[pete.y]

will that be costly then and do most garages do it?

 

[grahamcol]

If it's just a sensor then that shouldn't cost much. I'd be inclined to use a Merc specialist (not main dealer).

 

[television]

Most charge around £30 with STAR as you need to know where the fault is, it could be either of the fronts, or the rear one. Still could be the brake lamp switch.