When I first got the vehicle in 2007 the 4wd went out a few months after I got it. Fortunately, all I had to do was replace the switch panel for around $20. Maybe a year later, the 4wd stopped working again. So, I replaced the switch panel once again, but it didn't work. It won't come out of 4HI and the ABS light is on. I had a relative look at it back then and they mumbled something about a $500 computer part needing to be replaced. I know little to nothing about vehicles. Can anyone tell me what "computer part" this might be and if there is a cheaper alternative?

Thanks!