Hola, ya me fije en ese detalle del Access.
Es raro el comportamiento del Access, no debería pedir el parámetro C.indicecons.
Probá de esta manera:
Código SQL
[-]SELECT C.idcarro, C.nocarro, C.indececons, Sum(DHR.kmrecorrido) AS SumaDeKMRECORRIDO, Sum(CO.consumo) AS SumaDeCONSUMO
FROM carro AS C, hojaruta AS HR, deschojaruta AS DHR, consumo AS CO
WHERE (((CO.fecha) Between [:FECHA1] And [:FECHA2]) AND ((HR.idcarro)=[C].[idcarro]) AND ((DHR.idhojaruta)=[HR].[idhojaruta]) AND ((CO.idcarro)=[C].[idcarro]))
GROUP BY C.idcarro, C.nocarro, C.indececons
ORDER BY C.idcarro;
Saludos...