This is all pure BS. The Talon's PCM and i4WD computer have no idea what size tires you have on the machine. Plenty of folks have 30's and 32's without any problems other than the power they consume. I have an R with 16,000 miles and 32's and has never set a code. I have another with 3,500 miles with 30's and has only set a i4WD code once when I broke the RF knuckle and had to tow it with only 3 wheels on the ground (it didn't like that one bit).
i4WD code 7-1 simply means there is a tire size mismatch detected. The PCM isn't even smart enough to distinguish which tire is not matched. One of the 4 tires is a different size than the other 3. It detects this from the wheel speed sensors and if one of the fronts or the rears are not turning at the same speed (within a certain tolerance) it will set code 7-1.
This can happen for several reasons...
- You had a flat. The code will not reset itself, even after you fix the flat. You have to reset or no 4WD. You can reset it on the trail with a PCM jumper and the right procedure.
- One tire is larger than the others or the fronts are not the same size as the rears.
- Uneven tire pressure or too much front/rear pressure difference.
- Bad speed sensor (the Talon has 5). There isn't really a difference in tire size but one of the sensors is sending incorrect data to the control unit. I have seen several Talons with loose plugs (of all kinds). It would not surprise me one bit if one of your speed sensors was not properly plugged in and causing a code.
If all your tires are the exact same size on the exact same width rims, start by making sure your tire pressures is correct. You can run less pressure in the front because it front is lighter. I use the 45/55% rule for my pressures. I run my dirt tires at 10 front and 12 rear while trail riding and lower down to 5 front and 6 rear for rock crawling without any issues. I run my paddles at 5 front and 6 rear all day long, wide open throttle mostly in i4WD at 50 MPH without any issues.
If you run all same size tires on stock rims, you will have a little issue with the fronts being larger than the rears because the front wheels are narrower. You may have to play with tire pressures and measure the circumference at different pressures if this is your setup.
Larger tires can mess with the shift points and that is it. I believe Hess has a tire size compensation for their tunes, DynoJet does NOT. But, the DCT adapts to your tires and the way you drive. Give it a little time (a few hundred miles) and see if it corrects itself. Most with 30's and many with 32's find the DCT adjusts just fine and no tune is needed.