75MPH speedometer 90MPH scangauge

[Pee-wee German]

Oh you guys are gonna love this:

- I was going 75MPH for 15 minutes just now, it felt a bit windy so I took my eyes and hands off the road (oh relax; my knee can hold the wheel) while i checked the scangauge. I was traveling at 90MPH the whole time.

-is the speedometer broken since the 2.0 update 2 weeks ago? -My TPMS keeps alerting me every 5 minutes, but my tires are at 40psi. Maybe it's my whole computer ready to die?

[SuperGeek]

The Scangauge gets its info from the computer. The speedometer, I'm not sure if it's the same source or if it's tied straight to the wheels like in the olden days. To get a 99% accurate speed measurement, get on a highway at what you think is 60mph, then count how many seconds it takes to go between mile markers. 60mph = 1 minute, 90 mph = 40 seconds. 75mph = 48 seconds

Or try GPS. If you have an iphone, download the InstaMapper GPS Tracker application which is pretty accurate.

If you were just at the dealer, and they did ECU work just prior to some weirdness, definitely call them about it.

[jimvw57]

The speedo gets the info from the same place. Find a local police car using a radar gun and ask them. They are usually pretty helpful. Or get a buddy to pace you in another vehicle, that should give you a good indication well within 15MPH.

Best thing is to get in touch with the dealer. They do have a service network that can at least identify if the problem has happened before.

[Brabus007]

Use your GPS for a independent accurate Speed Report...YUP

[John_H]

smartacus - have you altered your instrument cluster in any way such as putting in custom graphics for the speed indication?

I'm sure they've covered in the other thread that the TPMS is relative, needs to be reset to a "baseline" and will give a TPMS error if one of the sensors has failed. But the speedometer being off suggests to me there's a mechanical problem with the stepper motor and needle assembly. Either that or your tires are significantly different in diameter from stock.

My 2.0 upgrade and multiple accesses to the innards of the instrument cluster still leave me with the ~2mph high reading that I've had all along (and saw in my previous car as well).

[mrc59]

I have done nothing to the drivetrain. But my spedo reads low compared to the GPS. At 50MPH on the speedo, the GPS says 48.

[LittoDeviL]

Originally Posted by mrc59

I have done nothing to the drivetrain. But my spedo reads low compared to the GPS. At 50MPH on the speedo, the GPS says 48.

That's about right, the speedometer usually is about 2-3 mph "faster" then the actual speed. I wont get into details why they do this but it's setup that way.

On my scangauge it shows the actual speed of the road while the speedometer shows a few miles per hour over.

Larry

[Pee-wee German]

Originally Posted by John_H

smartacus - have you altered your instrument cluster in any way such as putting in custom graphics for the speed indication?

I'm sure they've covered in the other thread that the TPMS is relative, needs to be reset to a "baseline" and will give a TPMS error if one of the sensors has failed. But the speedometer being off suggests to me there's a mechanical problem with the stepper motor and needle assembly. Either that or your tires are significantly different in diameter from stock.

My 2.0 upgrade and multiple accesses to the innards of the instrument cluster still leave me with the ~2mph high reading that I've had all along (and saw in my previous car as well).

No mods of any kind. stock everything. completely bone stock.

[fastturb]

It sounds like a kph vs mph thing to me.....

[ArthurRW]

I noticed that "Maggie" my Magellan 1475T reads less than my speedo by about 2-3 mph. I wonder if the odometer is off by a similar amount since the old cable type speedo/odo units got their input from the same place.