FORScan on a Gen1

Humvee21 said:

Has the nav bypass successfully worked on a 2012?

Also, would changing tiresize in FORScan correct speedo and odo for 37" tires?

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DrewFish11 said:

Also wondering about the nav bypass for my 2013. Haven't come across it yet.

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Crikk said:

Is this able to turn off my rear parking sensors. Also if you can adjust tires size would that help with my navigation being off on the truck location

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Darick said:

How would adjusting your tire size change your GLOBAL POSITIONING SYSTEM? I guess satellites now get their readings from your speed sensors.

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t_j said:

Well the truck uses whats called A-GPS (Assisted Global Positioning System). This type of GPS implementation is common in the automotive and cell phone GPS markets. In the automotive sector they use the speed sensors to augment the GPS data to make your location more accurate, this is especially important when you need fine grain location information that is more accurate than a pure GPS signal such as when approaching and intersection. In cell phones its used provided faster initial location dead reckoning, to do this they use databases of cell tower locations and wifi hotspot locations. The phone keeps track of towers and hotspots it can see and uses that information with the database of locations to speed up initial location fix when GPS is first activated. The automotive sector doesn't need this type of assistance as vehicles tend not to move when they are not turned on.

So back the the tire size, if it's wrong the truck will be traveling faster or slower than than the computer thinks it is because the truck uses the wheel speed sensors or transmission output shaft speed to calculate the speed the truck is moving. Due to this the GPS slowly accumulates an error as its moving putting the GPS position further ahead or behind of the actual location depending on which way way the tire size was changed.

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Darick said:

In no area have I found anything regarding Ford using A-GPS. I'm only finding data that this is used in cellular platforms only. Do you have any sources for this information, as I'm curious to how it's linked and functions on the Ford Sync platform.

Ford may be using dead reckoning, which would calculate off speed signals, but that should only kick in when you're in a tunnel, parking garage, or in a forest. There are multiple other Ford forum posts that recommend disconnecting the negative cable and letting the car sit for 1 hour, and this has resolved multiple issues (pre and post tire recalculation).

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