IDOC Error with STATUS 51

HI,

I has a JMS-XI-IDOC Scenario where i has used BPM to get the response from RFC wehre the RFC input is the message from JMS.

The Response Message from RFC is mapped to IDOC .The Scenario is working and the IDOC is getting created in SAP System Iam getting the Error with Status = 51 and the required field LIFNR not found.

Request you to please provide the suggestion whether i need to make any settings to resolve this.

Thanks & Regards,

Y.Raj.