Error making an API call through postman for generating access token with grant type "password"

[Archie]

HI,

I am trying to make an API call through postman for generating access token with grant type "password", but getting error "{"ErrorCode" : "invalid_client", "Error" :"Client identifier is required"}", even I am passing username and password in body section and client_id and secret in request header.

<Flow name="Generate Access Token Password">
<Description>flow for generating access token using password grant type</Description>
<Request>
<Step>
<Name>OAuth_V2_Generate_Access_Token_Password</Name>
<Condition>(proxy.pathsuffix MatchesPath "/access_token_password") and (request.verb = "POST")</Condition>
</Step>
</Request>
<Response/>
</Flow>

Below is the Oauth policy I am using,

<Operation>GenerateAccessToken</Operation>
<SupportedGrantTypes>
<GrantType>password</GrantType>
</SupportedGrantTypes>
<GrantType>
<UserName>username</UserName>
<PassWord>password</PassWord>
</GrantType>
<GenerateResponse enabled="true"/>