What software would I have to buy to program a new body control module

Hello, Dave here, contributing to RepairPal and providing expert advice since 2010. To answer the question in your subject line, you would need to have diagnostic software for Dodge vehicles. This would be prohibitive to purchase for single use. Repair shops spend thousands of dollars on diagnostic tools and the purchase of software licensing. When you saw the voltage fluctuating, was it on the dash voltmeter? It sure sounds like you have a battery and / or power supply issue. This should be checked by checking your battery first for state of charge and the ability to sustain a load. From there, with a known good battery, the rest of the charging system should be checked. Are there any added on aftermarket parts on this vehicle? This should be considered also, in that it could cause power surges and voltage drops. Reach out to a shop near you for further guidance and hands on testing assistance. https://repairpal.com/auto-repair-near-me Click the link or call us at 877-913-1554. We'll gladly find you a certified RepairPal shop in your area.