repeated SIT problems are usually battery related, if you are certain that the battery is good, remove it and check for cable problems on the cables to the drive motor (melted together or rubbed / smashed.) if none of those are the problem it gets more complex...diodes, snubbers, cpu and dcsd boards. also you need to replace all three at one time. (very pricey) if you have transistor controlled lift you can get creative with some swapping but once overamp'd they're going to fail at some point.