invalid oauth token

invalid oauth token

Hi Folks,

I am generating grant token using uri redirect(https://accounts.zoho.in/oauth/v2/auth?scope=ZohoCRM.users.ALL&client_id={client_id}&response_type=code&access_type={"offline"or"online"}&redirect_uri={redirect_uri})

after that using grant token iam generating auth token by post method by passing clientid,clientsecret,code(granttoken)...etc in the body then iam able to generate  bearer token which is required to make get/post calls . 

But when i am using this token for Get method its throwing me an error 
Iam passing it as header like Authorization: Zoho-oauthtoken 1000.4xxxxxxxxxxxxxxxx.5exxxxxxxx
{
    "code": "INVALID_TOKEN",
    "details": {},
    "message": "invalid oauth token",
    "status": "error"
}
Please guide me how to make get/post calls using oauthtoken.