Message type: E = Error
Message class:  BG - Warranty processing 
Message number: 073
Message text: Select at least one service item
Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of messages in the SAP system have a message text, however this is frequently insufficient to comprehend or resolve the problem.
To make things easier, more detailed information is frequently added to describe the issue, how to fix it, and the necessary steps or configuration modifications.
Unfortunately, there isn't any extra information in this error notice.
First, use our AnswerBot below to get a possible cause and solution (requires a premium subscription).
Also, review the in-depth Common Questions & Answers listed below; you could discover a solution there or be able to connect with others who have faced similar challenges.
You can also try searching the SAP support portal (support.sap.com) but you need a special user ID to access it. It is possible that an SAP support note exists that provides additional details about the mistake or even steps for fixing it.
The SAP error message BG073 ("Select at least one service item") typically occurs in the context of service-related transactions, such as when creating or processing service orders, service confirmations, or service-related billing documents. This error indicates that the system expects at least one service item to be selected or specified, but none has been provided.
Cause:
No Service Item Selected: The most common cause is that the user has not selected any service items in the transaction screen where service items are required.
Incorrect Configuration: There may be issues with the configuration of service items in the system, leading to them not being available for selection.
Data Entry Error: Users may inadvertently skip the selection of service items due to oversight or misunderstanding of the transaction process.
Solution:
Select Service Items: Ensure that at least one service item is selected in the relevant transaction. This can usually be done by checking the list of available service Get instant SAP help. Sign up for our Free Essentials Plan.
Get instant SAP help. Sign up for our Free Essentials Plan. 
BG072 Configuration: Error while locking service &
What causes this issue?  A system error occurred in locking a service.System Response  The system issues an error message and will not allow you to co...
BG071 Configuration: Service & may not be configured
What causes this issue?  You entered a service that cannot be configured. The system issues an error message and will not allow you to continue with t...
BG074 Configuration data to & will be lost
What causes this issue?  You created configuration data for the service item, but terminated processing without saving first.                         ...
BG075 Configuration changes for & will be lost
What causes this issue?  You changed the existing configuration data for the service item, but terminated processing without saving first. The system ...
Click on this link to search all SAP messages.