Error while executing Split Function

Create function dbo.fnSplit_Vehicle
(@sInputList varchar(100), @sDelimiter varchar(1))
returns varchar(100)
--select dbo.fnSplit_Vehicle ('1234 abcd', '-')
AS
BEGIN

Declare @Domain varchar(100)

set @Domain = RTRIM(LTRIM(SUBSTRING(@sInputList,1,CHARINDEX(@sDelimiter,@sInputList,0)-1)))

return @Domain

End

Msg 537, Level 16, State 2, Line 1
Invalid length parameter passed to the LEFT or SUBSTRING function.