JScan Tire Size Issues [Help]

huntb

Active Member
First Name
Ben
Joined
Apr 19, 2020
Messages
28
Reaction score
9
Location
Michigan
Vehicle(s)
18 JLUS, 14 WK2 EcoDiesel
I changed my tire size using JScan and then the dealer must have flashed over it when they reprogrammed my radio. I thought it just reset it and I would need to reprogram them again, but now the speedo is ~3% fast, which would mean the computer thinks the tires are larger than what they are, not back to stock.

Does anyone know how to reset everything back to stock so I can reprogram to the correct size?





Advertisement

 

Stuckinthesand

Well-Known Member
First Name
CJ
Joined
Apr 6, 2020
Messages
322
Reaction score
220
Location
NJ
Vehicle(s)
2019 Wrangler sport s 2017 GMC Acadia
You have to select the stock tire size. It says 31.25 factory in the app.
 
OP
huntb

huntb

Active Member
First Name
Ben
Joined
Apr 19, 2020
Messages
28
Reaction score
9
Location
Michigan
Vehicle(s)
18 JLUS, 14 WK2 EcoDiesel
  • Thread starter
  • Thread Starter
  • #3
Resetting it back to stock got it close to what it should be, but it is still off. I'm asking if there is a way to reset the module, where tire size information is stored, back to default.
 

Stuckinthesand

Well-Known Member
First Name
CJ
Joined
Apr 6, 2020
Messages
322
Reaction score
220
Location
NJ
Vehicle(s)
2019 Wrangler sport s 2017 GMC Acadia
As far as I know there is now way to reset it back to default with JScan. You can try to do an ecu reset and that may work. I’m a little confused. Are you running stock tires or larger tires?
 
OP
huntb

huntb

Active Member
First Name
Ben
Joined
Apr 19, 2020
Messages
28
Reaction score
9
Location
Michigan
Vehicle(s)
18 JLUS, 14 WK2 EcoDiesel
  • Thread starter
  • Thread Starter
  • #5
As far as I know there is now way to reset it back to default with JScan. You can try to do an ecu reset and that may work. I’m a little confused. Are you running stock tires or larger tires?
I'm running rubi take offs on my Sahara and programmed it with JScan to correct for the larger tires. I then had some dealer work done because my UConnect was acting up without changing the tires back to stock. They must have overwritten something because the speedo was acting like there were 34 or 35's on when I got it back. JScan still showed the 32.5" that I had set it with. I changed it back to the stock 31.25 with JScan and it helped, but the speedo is still slightly off
 

Stuckinthesand

Well-Known Member
First Name
CJ
Joined
Apr 6, 2020
Messages
322
Reaction score
220
Location
NJ
Vehicle(s)
2019 Wrangler sport s 2017 GMC Acadia
I'm running rubi take offs on my Sahara and programmed it with JScan to correct for the larger tires. I then had some dealer work done because my UConnect was acting up without changing the tires back to stock. They must have overwritten something because the speedo was acting like there were 34 or 35's on when I got it back. JScan still showed the 32.5" that I had set it with. I changed it back to the stock 31.25 with JScan and it helped, but the speedo is still slightly off
Ok now I understand. That’s weird. I know even though I’m running 35’s I had to set the tire size to 33.5 with JScan to get my speedo dead on. Maybe take it down one more size to see if it gets the speedo correct. I have an auto and even though it’s programmed at 33.5 it still shifts gears like normal. Only other thing I can think of is to disconnect the batteries or pull the ecu fuses to reset it.
 
OP
huntb

huntb

Active Member
First Name
Ben
Joined
Apr 19, 2020
Messages
28
Reaction score
9
Location
Michigan
Vehicle(s)
18 JLUS, 14 WK2 EcoDiesel
  • Thread starter
  • Thread Starter
  • #7
Ok now I understand. That’s weird. I know even though I’m running 35’s I had to set the tire size to 33.5 with JScan to get my speedo dead on. Maybe take it down one more size to see if it gets the speedo correct. I have an auto and even though it’s programmed at 33.5 it still shifts gears like normal. Only other thing I can think of is to disconnect the batteries or pull the ecu fuses to reset it.
Good to know, thanks. I'll give your suggestions a try and report back. The dealer also didn't fix my radio issues either, so I plan on taking it back and will have it reset to stock before I go
 

Robicon-JLU

New Member
First Name
Rob
Joined
Jan 31, 2021
Messages
4
Reaction score
6
Location
Ottawa
Vehicle(s)
2021 Wrangler Unlimited Rubicon
Ok now I understand. That’s weird. I know even though I’m running 35’s I had to set the tire size to 33.5 with JScan to get my speedo dead on. Maybe take it down one more size to see if it gets the speedo correct. I have an auto and even though it’s programmed at 33.5 it still shifts gears like normal. Only other thing I can think of is to disconnect the batteries or pull the ecu fuses to reset it.
Sorry to be bringing up an older thread... just traded my JTR for a JLUR and moving from a Tazer to JScan. Same tires on the JL that were on the JT - 35". With the Tazer, I set them to 34.8" and the speedo was bang on. With the JScan, I set them to 34.75" (the closest to the 34.8") but the speedo reads quite a bit high now. Odd that I would have to set it to 33.5" to get the speedo accurate when the stock tires were 33". I asked JScan if there was an issue with their settings perhaps but they said no. Obviously there is something weird going on with those calcs.
 

Stuckinthesand

Well-Known Member
First Name
CJ
Joined
Apr 6, 2020
Messages
322
Reaction score
220
Location
NJ
Vehicle(s)
2019 Wrangler sport s 2017 GMC Acadia
Sorry to be bringing up an older thread... just traded my JTR for a JLUR and moving from a Tazer to JScan. Same tires on the JL that were on the JT - 35". With the Tazer, I set them to 34.8" and the speedo was bang on. With the JScan, I set them to 34.75" (the closest to the 34.8") but the speedo reads quite a bit high now. Odd that I would have to set it to 33.5" to get the speedo accurate when the stock tires were 33". I asked JScan if there was an issue with their settings perhaps but they said no. Obviously there is something weird going on with those calcs.
Yeah I’m not sure but I’d agree. I did measure like the JScan suggests in the help section and that came out to the 33.5”. They have you measure from the top of the tire to the ground. Maybe tazer goes off of stated tire size?

0C2503E6-68A2-4B0B-814E-618B67380033.png
 

WranglerMan

Well-Known Member
First Name
Will
Joined
May 8, 2018
Messages
2,465
Reaction score
1,650
Location
Katy Texas
Vehicle(s)
2018 Wrangler JLU Sahara
Occupation
Gas Pipeliner
Vehicle Showcase
1
Pay no attention to picking the correct size, measure the tire and plug that number in as close as you can get then do a reboot for the changes to take affect then take it out for a test drive and check the speedo with something like the Speedbox app and if its off then go back into Jscan and adjust up or down to get it closer, it takes a few times like I had to do it 3-4 times but my Speedo is only off by 1 mph running 35’s and my speedo is showing 1 mph faster than I’m actually going and that’s fine with me.

I had the same issue with the Tazer when I ran it, I had to put in 35.5” on a 34.75” tire to get the speedo correct so to me the choices in jscan and Tazer are just references and you have to tweak those numbers
 

Bigfx1

Well-Known Member
Joined
Dec 24, 2020
Messages
109
Reaction score
46
Location
Texas
Vehicle(s)
Jl rubicon
Anyone have an ess problem after resizing their tires? I have a six speed manual and I’m getting an ess fault
 

Redneck_Jedi

Well-Known Member
First Name
Charles
Joined
Jun 9, 2017
Messages
913
Reaction score
1,071
Location
WPB, FL
Vehicle(s)
2019 Jeep Wrangler Sport S 2 Dr.
Vehicle Showcase
1
Anyone have an ess problem after resizing their tires? I have a six speed manual and I’m getting an ess fault
No issues here. I have a V6 Auto.
 

WranglerMan

Well-Known Member
First Name
Will
Joined
May 8, 2018
Messages
2,465
Reaction score
1,650
Location
Katy Texas
Vehicle(s)
2018 Wrangler JLU Sahara
Occupation
Gas Pipeliner
Vehicle Showcase
1
Anyone have an ess problem after resizing their tires? I have a six speed manual and I’m getting an ess fault
Please clarify ESS fault, like what does the ESS message say on the EVIC display ?

I personally cannot see how changing the tire size with JSCAN would cause any issues with the ESS system.

The biggest thing with Jscan is it does not back up your stock configuration like the Tazer does it only looks at the current value from the ECU and allows you to change that parameter so what I do when I first stared making changes and still do is right down the current ECU value so if there is an issue I can go back and put that value back in but as I said I’m not quite sure how changing tire size would affect the ESS system
 

Bigfx1

Well-Known Member
Joined
Dec 24, 2020
Messages
109
Reaction score
46
Location
Texas
Vehicle(s)
Jl rubicon
Just to circle back on this when reprogramming tire size on manual transmission vehicles you have to let the vehicle re-learn the sixth gear ratio, take off battery cables then take the vehicle and get up to 40 and lay on the gas in sixth and it recalibrated everything.
 

WranglerMan

Well-Known Member
First Name
Will
Joined
May 8, 2018
Messages
2,465
Reaction score
1,650
Location
Katy Texas
Vehicle(s)
2018 Wrangler JLU Sahara
Occupation
Gas Pipeliner
Vehicle Showcase
1
Just to circle back on this when reprogramming tire size on manual transmission vehicles you have to let the vehicle re-learn the sixth gear ratio, take off battery cables then take the vehicle and get up to 40 and lay on the gas in sixth and it recalibrated everything.
I have never heard of this, I have the A/T 3.6 and as far as recal went after adjusting tires size the JL from my research relearns automatically but one has to do a few power off/on cycles and with Jscan or Tazer it’s pretty easy to do this without removing cables from the batteey.
 

Advertisement




Allmoparparts.com
 



Advertisement
Top