As per Section 17(5)(a), input tax credit shall not be available in respect of the following, namely:-
"(a) motor vehicles for transportation of persons having approved seating capacity of not more than thirteen persons (including the driver), except when they are used for making the following taxable supplies, namely:-
(A) further supply of such motor vehicles; or
(B) transportation of passengers; or
(C) imparting training on driving such motor vehicles;"
And very same restrictions applies while taking ITC of 'Compensation Cess' as per Section 11 of the Goods and Services Tax (Compensation to States) Act, 2017.
As informed by you, your are manufacturer and not entitled to take ITC against vehicles purchase by you (presumably on account of restrictions by above-said Section 17(5)(a)). In such a situation, you can not taken ITC even against 'Compensation Cess' charged to you while purchasing these vehicles.
Just an addition information:
Wherever ITC against 'Compensation Cess' is available & taken by any tax-payer, as per proviso to Section 11 of the Goods and Services Tax (Compensation to States) Act, 2017, 'the input tax credit in respect of cess on supply of goods and services leviable under section 8, shall be utilised only towards payment of said cess on supply of goods and services leviable under the said section.'
These are ex facie views of mine and the same should not be construed as professional advice / suggestion.