Under legislation approved 51 to zero, the $1,000 fees would fall to about $600 next year and $400 a year later.
The fees were increased last year to help balance the state budget, but they proved unpopular. Some companies said they were being driven out of business.
Lawmakers say last year's change created a loophole that exempted Hummers and other big SUVs from sales taxes, a $22 million savings.
That loophole would be eliminated under the new proposal, which now goes to the Illinois House.