Speedometer not reading correctly

[jnmarshall]

The other day on the highway I had my cruise set for 70mph. I looked at my speedo and it was around 73-74. I paged thru the MFD and pulled up the current speed and it showed 70. After that I left it ther and noticed my speedometer was progressively off starting at about 40mph
MFD=40. Speedo=41
MFD=50. Speedo=52
MFD=60. Speedo=63
MFD=70. Speedo=74
Etc...

Shouldn't the speedo be getting the same signal as the MFD?

 

[Jeffbucc]

Does this happen repetitively? Or was this just a one time occasion. Is the cruise control number higher than your actual speed too?

Mine did this too after I played around in vag-com for a bit and when away then next day.

 

[dcullen]

This is by design. The speedometer will read a bit faster than actual vehicle speed. This is in response to various laws (mostly European) that require that speedometers must never display less than actual speed. This provides a small cushion for errors in dial, slightly oversized tires, etc.

 

[jet_a]

Have you messed with snow tire mode? Check MFD and make sure you have the correct setting for the size tire you have on. Speedometer should show 1 mph faster than actual speed [at any speed], and cruise should show actual speed.

 

[jnmarshall]

Does this happen repetitively? Or was this just a one time occasion. Is the cruise control number higher than your actual speed too?

Mine did this too after I played around in vag-com for a bit and when away then next day.

Consistently behaves this way. I played with VCDS last nite for the adjustment and compared to a GPS. Still get the same error rate between the two. The VCDS settings seems to just adjust the vss pulse to both.

 

[jnmarshall]

This is by design. The speedometer will read a bit faster than actual vehicle speed. This is in response to various laws (mostly European) that require that speedometers must never display less than actual speed. This provides a small cushion for errors in dial, slightly oversized tires, etc.

It doesn't appear to be designed this way in other Jetta's. My sedan doesn't have this issue and neither did another JSW at the dealer lastnite. Service department believes they need to replace it and I figured I would wait till the 10K appt. I only have 1300 on it now. I'm assuming the actual mileage calculations are using the MFD numbers.

 

[jnmarshall]

Have you messed with snow tire mode? Check MFD and make sure you have the correct setting for the size tire you have on. Speedometer should show 1 mph faster than actual speed [at any speed], and cruise should show actual speed.

Snow tires is off.

 

[cd_booth]

Have you messed with snow tire mode? Check MFD and make sure you have the correct setting for the size tire you have on. Speedometer should show 1 mph faster than actual speed [at any speed], and cruise should show actual speed.

"Snow tire mode" is only another speed warning. It does nothing to adjust speedometer readings.

 

[Johnny G1]

Don't feel bad, mine is out 8% and they seem to think that is normal, got stopped for driving to slow and the cop wanted to know why I was driving about 16K under the speed limit, @100k the speedo shows 108 against a GPS. Just my thoughts, VW don't don't seem to care either way. Just BS.

 

[Jeffbucc]

I switched mine to transporter instead of jetta/golf and it is dead on after using two different gps's/ I noticed it will stay in the same if you switch the region to GB or RoW.