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It can usually be done with a scan tool. (Pinion factor). I have not specifically check on the WiTECH2. You can do it with a Diablosport trinity.
Product Features



  • Add Horsepower, Torque, and Fuel Economy to your 2015+ Chrysler Vehicle!
  • Factory Modified PCM that allows a 15+ Chrysler vehicle to be tuned
  • Installation is simple and only takes about 10 minutes
  • Swap with your factory installed PCM so you always have a back up computer
  • Includes a DiabloSport Trinity T1000 Tuner & Monitor in the box.
  • Touch Screen
  • 93 Octane Performance Tune: 10HP 10TQ
  • 91 Octane Performance Tune: 8HP 8TQ
  • Calibrate Speedometer for Gear Ratio
  • Calibrate Speedo for Tire Size
  • Cooling Fan Control
  • Disable ESP
  • Throttle Booster
  • Fuel Rich/Lean Adjustment
  • Spark Timing Advance/Retard
  • Idle RPM
  • Top Speed Limiter
  • Rev Limiter
  • Torque Management Adjustment
  • Disable Active Fuel Management
  • TPMS Adjustment
  • Reset TCM Adaptation
  • Disable Skip Shift
  • Disable Autostick Auto Upshift
Tom.
 

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Discussion Starter #3
I looked at the Diablo but it's a lot of money for just a speedo adjust. I know it does a lot of other things also and I am sorely tempted to get one but was hoping for one of those, "Yeah just simply ......." but know better, lol. It's not like I need more horses as this scat pac is plenty hp as it is! Even with the larger softer compound tires it will break loose from a standing start.
 

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Big tires just on the rear? I thought the speedo picked up from the front wheel on 2015+.


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These are GREAT machines. When I get the opportunity, I will hook up the WiTECH2 and see if the tire size is adjustable. If it is, a quick flash adjust may be possible. I also want to see if I can adjust my TPMS trigger pressure. lol! I drive around with my TPMS light on all the time because I run with 28-30 PSI in my rear tires. First cold day and the tire light comes on! We also have a MODIS but I am not sure if it is updated to 2015 yet! I will check. Lots of shops use the SnapOn system.
Tom.
 

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And the speedometer reads off the rear tires..
I just had a chance to pull up the configuration parameters on the WiTECH2 and the tire sizes can be adjusted.
It does say to return to factory tire size the original configuration must be reinstalled. (Reprogram module)
So you just need to find a shop with WiTECH2 and they can do it. (WiTECH2 is dealer level hardware)
I assume you are too far away from us here.
Tom.
 

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Please keep us posted. I am interested to see what I need to do to change tire size. I did also find out I can adjust my TPMS pressure threshholds, which I really wanted to do! I run my rear tires lower than the computer tolerates! lol!
Good luck!
(PS Chrysler only allows access to WiTECH2 from registered IP addresses. Besides, the system is my bosses! lol!)
Again, keep us posted please!
Thanks
Tom.
 

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Discussion Starter #15
I have an appointment with the dealer the 3rd and they are going to fix the issue. I did find that the speedometer is driven from the front tires. I will let you know what they do to correct the problem. I was joking about the use of your module.

Be well,
Steve
 

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Discussion Starter #16
Just got back from the dealer. It cost me $114 for them to change the tire size in the PCM/Sensors. The largest tire size they are allowed is 275 and I have 295s. But instead of being 4-5 mph off I am now a shade under 2 mph. Below 45 it is right on and up to 65 it is 2 with the occasional flicker to 66 from 67 on the gps unit. Once it gets up over 70 it is 2-3 mph off. I think the gps struggles a bit as does the car. Uphill the speedo reads a bit low and downhill a bit high but the gps shows it as fairly steady.

The way the speedometer reads is thus: There are sensors in the front and rear as well as one on the driveline. All of them have an impact on what the speedometer reads. Changing the pinion angel, larger tires on the rear, changes how the driveline sensor reads speed. It's a unique system that the factory settings can't fully accommodate due to tire size limitation. But the $114 to have the PCM flashed for this is a lot cheaper than $229 for one I would own and is no good to any other VIN than mine is well worth it. This is the tire size I plan on running as long as I own the car so it's half the cost and Dodge warrants it. If it starts to have problems they redo it for free.

The service man today was very friendly and worked really hard to meet my requests. Last time he must have been having a bad day as I didn't care for him or his attitude. We talked about aftermarket PCMs and running them and putting the stocker in when coming in for service work and there is apparently no way for them to know that you have installed an other than factory option. But that is for another thread.
 

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Just got back from the dealer. It cost me $114 for them to change the tire size in the PCM/Sensors. The largest tire size they are allowed is 275 and I have 295s. But instead of being 4-5 mph off I am now a shade under 2 mph. Below 45 it is right on and up to 65 it is 2 with the occasional flicker to 66 from 67 on the gps unit. Once it gets up over 70 it is 2-3 mph off. I think the gps struggles a bit as does the car. Uphill the speedo reads a bit low and downhill a bit high but the gps shows it as fairly steady.

The way the speedometer reads is thus: There are sensors in the front and rear as well as one on the driveline. All of them have an impact on what the speedometer reads. Changing the pinion angel, larger tires on the rear, changes how the driveline sensor reads speed. It's a unique system that the factory settings can't fully accommodate due to tire size limitation. But the $114 to have the PCM flashed for this is a lot cheaper than $229 for one I would own and is no good to any other VIN than mine is well worth it. This is the tire size I plan on running as long as I own the car so it's half the cost and Dodge warrants it. If it starts to have problems they redo it for free.

The service man today was very friendly and worked really hard to meet my requests. Last time he must have been having a bad day as I didn't care for him or his attitude. We talked about aftermarket PCMs and running them and putting the stocker in when coming in for service work and there is apparently no way for them to know that you have installed an other than factory option. But that is for another thread.
Thank you for the update! That is good information to know!

Be well.

Tom.
 
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