anyone else have any issues with there speedometers reading wrong. i've noticed that my speedometer reads 4mph fast. i thought it was due to the tires that were on the car when i bought being bald, but thats not the case as i have replaced them. what's it take to have it recalibrated. trip to the dealer?
Speedometer reading wrong
- Thread starter tightgtp
- Start date
Seatman
Top Post Dawg
That's normal on these cars wether on your side of the pond or my side, you can alter it through vagcom but I don't know what the settings are, you could try a search on here but personally I don't mind as it means I'm less likely to get a speeding ticket.
icecap
Veteran Member
- Joined
- Apr 10, 2007
- Location
- Chilliwack & Mission BC
- TDI
- 2006.5 Jetta TDI 5Spd Black Anthracite Pkg 1
This issue has been beaten to death and still crops up on occasion prompting a load of responses from dismantling your cluster and repositioning the needle, changing tire size, and heaven forbid, recoding the speedometer with VCDS. That usually brings cries of it will mess up your odometer accuracy and the wheels will fall off. The truth of the matter is that VW acknowledged that there was an issue and released a TSB in early 2007 instructing dealers to recode the speedometers of every new 2007 vehicles in their inventories. That TSB was followed by TSB 90 07 03 May 24, 2007 #2012684 which permitted the previous dealer TSB to be performed on all A5 vehicles prior to 2007. The TSB clearly indicates that the recode does not alter the odometer accuracy.
Nuff said for the umpteenth time.
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Seatman
Top Post Dawg
New people come along all the time though so it's inevitible that the same stuff will come around again and again, I didn't have a clue about using the search function or any of that when I first started using these forums so I don't mind as long as people are polite and not trying to cause trouble.
sorry man to bring it up again, but any search i did on this forum brought no such thread about speedometer being wrong. now given the fact that i might try for two or three times to do a search with specific keywords being speedometer and nothing coming up i'm safe to assume it hasn't been asked. prove me wrong i'd love to see a thread relating to it.
D-Cell_Mekanick
Veteran Member
Here's a few threads:
http://forums.tdiclub.com/showthread.php?t=307947&highlight=Speedometer
http://forums.tdiclub.com/showthread.php?t=158652&highlight=Speedometer
http://forums.tdiclub.com/showthread.php?t=309703&highlight=Speedometer
http://forums.tdiclub.com/showthread.php?t=272676&highlight=Speedometer
http://forums.tdiclub.com/showthread.php?t=287507&highlight=Speedometer
There are many many more thread about this.
http://forums.tdiclub.com/showthread.php?t=307947&highlight=Speedometer
http://forums.tdiclub.com/showthread.php?t=158652&highlight=Speedometer
http://forums.tdiclub.com/showthread.php?t=309703&highlight=Speedometer
http://forums.tdiclub.com/showthread.php?t=272676&highlight=Speedometer
http://forums.tdiclub.com/showthread.php?t=287507&highlight=Speedometer
There are many many more thread about this.
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Soooo....is there a charge for the dealer to do this??? My guess is yes, since it's not a recall...but I'm sure you'll correct me if I'm wrong.
ZiggyTheHamster
Veteran Member
Compared to what?
Don't compare your speedo to your GPS. Your GPS has error introduced into it intentionally by the government to prevent civilians from being able to precisely pinpoint a target. The error is random, but around 10 meters. If you ever notice that when you exit sometimes, it says you're still on the highway for a few seconds. This is because your location is still being read as on the highway due to the randomized error.
I don't have specific numbers but I would not be surprised if a GPS was anywhere from 3-7 MPH off. And I notice mine isn't always the same amount of off.
Unless you measured it with something that measures the wheel rotation, assume it's right if the TSB has been applied or is not applicable.
GibMir1
Veteran Member
Ziggy said "Unless you measured it with something..." Whenever I see one of those mobile radar stations, I'll note my speed and compare it to the display. I've found my speedometer is off on the high side about 5% - 6% (Not MPH).
D-Cell_Mekanick
Veteran Member
Ziggy when I found my speedo off by 4 mph (I forget at what speed it started to be inaccurate) I used GPS, radar station, another vehicle, and the average speed on the mfd, set the cruise at 60(according to the speedo) then reset the mfd. Turned out the speedo read 4 mph off! I then took it into VW for some warranty work and told them they supposably had done a tsb on it and now it only reads 3 mph higher, lol. Again verified by all four methods.
Your gps theory holds water on location, but not on speed.
Your gps theory holds water on location, but not on speed.
ZiggyTheHamster
Veteran Member
Radars are only accurate to about 4 lanes across, because once you get that far away, the beam is larger than the vehicle. I think that's around 100 feet or so. Also in OK at least, all of the radar things say I'm going faster than my GPS and speedo indicate. Obviously you have the opposite problem
I'd say that's enough testing to deduce that it's off. Just don't depend solely on the GPS.
There's some tuning (I think it's called the impulse number or something to that effect) that you can do with VCDS; they probably incremented that number. That sort of works around the issue, though it doesn't solve it. And the way that number works the way I understand is that your car now thinks you have larger tires than you do.
Not sure the correct way to fix this, because if you make the speedo show it correctly mechanically by moving the needle, your MFD will still be wrong.
To calculate speed, your GPS is sampling your current location and determining how fast you're passing through the points it samples. If your current location has error randomly added to it, there'll be error introduced into your speed. I wouldn't think the error would be any more than 2-5 MPH though.
Tim Birney
Veteran Member
The 2005.5 TDI has a digital Speedometer (Subset of the Climatronic "Cheat Screen") that tracks the actual speed to the .5 MPH. Compared to GPS, it matches 100%, and both the Digital Speedometer, and the GPS show the same fault in the "Analog" Speedometer, I.E. the 3.5/4.0 MPH Difference in speed.
Now to the Guv'ment creating a fault in the GPS, I say BUNK. Any fault in any GPS, Consumer GPS Receiver, would be in the quality of components, and the tolerance(s) of said components.
Please keep in mind that all Telecommunications Companies derive the Timing for their Switches/T-1/T-3/OC48 and up Systems from, you guessed it, the GPS Satellites.
Now to the Guv'ment creating a fault in the GPS, I say BUNK. Any fault in any GPS, Consumer GPS Receiver, would be in the quality of components, and the tolerance(s) of said components.
Please keep in mind that all Telecommunications Companies derive the Timing for their Switches/T-1/T-3/OC48 and up Systems from, you guessed it, the GPS Satellites.
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ZiggyTheHamster
Veteran Member
The US government GPS system has a capability called selective availability, which introduced a cryptographically random error. Evidently it worked unlike I thought and each GPS gets the same amount of error, though that error cycles or something to that effect. The important thing is that they turned this OFF in 2000, so I'm wrong about that, and GPS is probably not that bad for testing your speedo.
That said, from what I understand, civilian receivers can only get a "coarse" signal, which samples ten times slower than the military "precise" signal. Though it seems that this error introduced by the sampling rate is only 3 meters if you're standing still. And looking at some GPS chipsets, it seems like they only do 4-10 samples per second. Most serial devices (of which a GPS chipset might be) run at 9600 baud (1200 bytes/sec), so 10 samples/sec would mean each packet is at most 120 bytes, which seems plausible.
On the way to work, I tried this out: At 55 MPH, my speedo and my GPS indicate 55 MPH. At 65 MPH, my GPS indicates 66 MPH. At 70 MPH, my GPS indicates 71 MPH. So I think it might be safe to say that the faster you go, the less accurate your GPS will report your speed - it can't increase its sampling rate, even though you are moving more feet per second.
If there's a measuring block for current speed (there must be if Climatronic can show it), it's probably a better idea to monitor that and adjust the needle accordingly. Once those are matched up, tuning the impulse number should get it to reality, which should really be measured with something that can read wheel speed.
That said, from what I understand, civilian receivers can only get a "coarse" signal, which samples ten times slower than the military "precise" signal. Though it seems that this error introduced by the sampling rate is only 3 meters if you're standing still. And looking at some GPS chipsets, it seems like they only do 4-10 samples per second. Most serial devices (of which a GPS chipset might be) run at 9600 baud (1200 bytes/sec), so 10 samples/sec would mean each packet is at most 120 bytes, which seems plausible.
On the way to work, I tried this out: At 55 MPH, my speedo and my GPS indicate 55 MPH. At 65 MPH, my GPS indicates 66 MPH. At 70 MPH, my GPS indicates 71 MPH. So I think it might be safe to say that the faster you go, the less accurate your GPS will report your speed - it can't increase its sampling rate, even though you are moving more feet per second.
If there's a measuring block for current speed (there must be if Climatronic can show it), it's probably a better idea to monitor that and adjust the needle accordingly. Once those are matched up, tuning the impulse number should get it to reality, which should really be measured with something that can read wheel speed.