Need to reset ECU's after updating tire size with JSCAN?

boontis

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I have been searching for an answer but haven't seen anything specific for JSCAN. I updated my tire size using JSCAN and it appears to have saved.

I've since read a few posts talking about "mashing the pedal a few times" off the line to get it to "relearn" shift points and also some people talking about overall performance based around the Jeep "learning" how we drive.

Is there any truth to these claims and should I be resetting ECU's now that I've got bigger tires? Will resetting ECU's cause any problems?





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Stuckinthesand

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I use the JScan. No need to do anything other than set tire size. Drive like you normally do and it will relearn your shift points based on your style. I use JScan for a few other settings and have never had to reset ECU’s.
 
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boontis

boontis

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I use the JScan. No need to do anything other than set tire size. Drive like you normally do and it will relearn your shift points based on your style. I use JScan for a few other settings and have never had to reset ECU’s.
Great info - thank you!
 

helloyello

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Hey, I have a couple of questions.. I am looking into this JSCAN situation,
a) because I just put on bigger tires, need to adjust the speedo
b) I am going to be upgrading the halogen lighting(headlights and fender) up front to LED.
is this what need? I found a cable and code reader that were 100$ each, do I need to buy the expensive ones? Also how hard is it to program things like the DRLs
Thanks, Jake
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BlackGenesis

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Hey, I have a couple of questions.. I am looking into this JSCAN situation,
a) because I just put on bigger tires, need to adjust the speedo
b) I am going to be upgrading the halogen lighting(headlights and fender) up front to LED.
is this what need? I found a cable and code reader that were 100$ each, do I need to buy the expensive ones? Also how hard is it to program things like the DRLs
Thanks, Jake
Screenshot_20201026-144434_Amazon Shopping.jpg
No, buy exactly what you have in cart.
Expensive once will make no difference.

Lest expensive bypass wires are to be found in Ebay - $19. They are identical to $100 wires
 

helloyello

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No, buy exactly what you have in cart.
Expensive once will make no difference.

Lest expensive bypass wires are to be found in Ebay - $19. They are identical to $100 wires
cool, thanks.. I will check out eBAY..
 

Stuckinthesand

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cool, thanks.. I will check out eBAY..
It’s the same exact items I bought. No need for the expensive stuff. Search the forums for JScan there are a few for the leds. I didn’t do that or else I would help. Tip on tire size though. Just because it says 35 that doesn’t mean it’s the real measurement. Makes sure to measure from bottom of tire to center of rim and double that. It may need adjusted a little more to get speedo dead on.
 

Abnmarine

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I had to cycle my ignition on/off a couple of times for the new tire size setting to take place. I learned this the hard way by pulling over, trying a different setting and seeing that it never changed until I did this.
 
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boontis

boontis

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Interesting - I'll have to check mine again. My MPG has dropped down to 16 since installing the 35x12.50's and I'm wondering if the JSCAN change didn't stick. (that mpg is all short trips around town - no highway or freeway so I'm hoping it's better on the highway when I finally take it out!)
 

Stuckinthesand

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Interesting - I'll have to check mine again. My MPG has dropped down to 16 since installing the 35x12.50's and I'm wondering if the JSCAN change didn't stick. (that mpg is all short trips around town - no highway or freeway so I'm hoping it's better on the highway when I finally take it out!)
That sounds right for mpg. I get around 18 and that’s a mix of city/highway. 75% highway. If it’s a long trip I’ve got as high as 21 at 72-75mph. You’ll know if it didn’t hold the settings. Your Speedo will be way off.
 

Abnmarine

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Interesting - I'll have to check mine again. My MPG has dropped down to 16 since installing the 35x12.50's and I'm wondering if the JSCAN change didn't stick. (that mpg is all short trips around town - no highway or freeway so I'm hoping it's better on the highway when I finally take it out!)
I had my tires installed yesterday and used a speed app on my phone. I kept trying different sized tires in JScan and would drive on the interstate. After several changes the differences between the speedometer and the gps app never changed until I turned the engine off a second time. Previously I only turned it off once.
I was getting pissed thinking it wouldn’t work but finally did.
 

Stuckinthesand

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If I remember right it tells you to turn off the ignition and close the driver door for 5 minutes. I left the OBD reader connected during this time. I disconnected after time went by and it worked for me. Wonder why you are having an issue.
 

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