Why do I need an ESP reset after a front-end alignment?

You need to "synchronize" the toe with the steering input sensor to ESP controls.

Got some useful info from our Hunter Alignment Machine Tech about ESP and alignments. This applies to all ESP-equipped vehicles. If you have an alignment and toe adjustments are required and you have ESP the steering angle sensor must be adjusted or unusual ESP operation can result, not always but sometimes you can get unwanted operation. As of Jan 1st, 2012 every vehicle sold in the US must have ESP as standard equipment, and all Jeeps have it standard as of 2006. There have been some reports of irregular operation of ESP that have caused some issues. Firestone (nationwide) will have the ability to reset most steering angle sensors, the ones that cannot be done must be reset at a dealership as they require their specific scanners. Some vehicles will require the battery to be disconnected for the reset and a "battery saver" cannot be used to save stuff like radio memory or the reset will not work so if your vehicle has an "anti-theft" radio that requires a code to unlock make sure you have that code ready.