Docs / Mapper Errors

Understand a Mapper error

A Mapper diagnostic identifies the source location, a stable code such as E3402, and details about the particular expression or input. Use the code to find the explanation and suggested correction.

Find the complete reference

1. Open the Mapper function reference. No sign-in is required.
2. Expand All mapper error codes in the Reference pane.
3. Search by code, topic, or words from the message. Each entry explains what went wrong and what to do.

The catalog comes from the same definitions as the deployed mapper's function guidance. You can also download the complete Markdown reference or read the JSON catalog. These include syntax, validation, runtime, and built-in function errors.

Use the message and code together

The catalog describes the general condition; the diagnostic identifies the affected expression and input. Some problems are found as you type. Others depend on sample data and appear only when you run the mapping. Correct the expression or input, rerun it, and save a mapping test case when the result should stay stable.

These are errors in the incoming X12 Mapper language, not X12 interchange/997/999 validation codes or outgoing JSLT/XSLT diagnostics. API and infrastructure failures also have their own codes. If a code has more than one existing use, its catalog entry says so; use the function label in the diagnostic to choose the relevant explanation.