Benny posted on March 10, 2011 12:10
After I upgraded to larger tires, the speedo was off a little in the Jeep. The ESP/PCM programs in the JK's are very particular about actual wheel speed and what the dash is displaying. The computer gets confused and will actually fight the driver when it thinks it's doing 60, and the vehicle is actually doing 65. The computer will reduce power to try to get the numbers to match. This causes the driver to add more "input" to speed the jeep back up. AEV makes a plug in module to correct for new tire diameter, it's called the ProCal module. http://www.aev-conversions.com/products/procal_module/ It also allows me to turn on or off the daytime running lights, the annoying one touch lane change blinkers, clear DTC's, adjust tire and gear settings and the coolest part, using the dimmer switch to adjust the idle. 
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The ProCal uses small switches set in different combinations to determine what feature is changed. You just plug it into the OBD port, the horn honks and you're done. I found it very easy to use and within 5 minutes I had changed all the setting I wanted to in my Jeep.
Now the bad part.....for some reason I can't get the extended idle feature to work. From the instructions you have to follow the steps exactly for it to work. I tried several times with no success. I posted a thread on AEV and JKOwners forums asking for advice. I recieved several tips and suggestions and still have yet to get it to work. I've sent a e-mail to AEV asking for help so I'll update this when I get it all figured out.
All in all this is a great product and a must have for JK's with bigger tires. Just hope I can get the extended idle thing worked out because next to fixing the speedo that was the big feature I bought it for.
Update: Aparently there is a small software glitch in my Jeep that is preventing the ProCal from executing the high idle command. Jordan at AEV suggested I go to my local Jeep dealer and have my PCM and TCIM updated. After consulting with the jeep tech I think I'm going to wait abit to have this done. They want $105.00 just to update my Jeeps computer.