checksum

A checksum is a small value stored inside an ECU file that acts like a fingerprint for a block of data. If someone edits the data and does not update the checksum, the ECU can tell something is wrong — and may refuse to start, or worse.

checksum reads a file and checks whether its stored checksums still match the data. Each one comes back OK (matches) or STALE (does not match — the data was changed after the checksum was written).

Important

checksum only checks. It never fixes. Correcting checksums after a modification is done by your flashing/checksum tool (ECM Titanium, WinOLS, …) — OpenRemap deliberately leaves that to you.

When do I need it?

Before you flash anything. A tuned file with stale checksums can brick an ECU. Verify first.
After any modification. health flags stale checksums; run checksum to see exactly which scheme is stale.
On a downloaded file you do not trust. Most freely-shared dumps carry stale or stripped checksums — the command will tell you.

Try it (2 minutes)

openremap checksum my-file.bin

If the file's checksums are intact you will see lines like Bosch ME7 main checksum: OK. If something was edited after the checksum was written, the line says STALE. Files of families OpenRemap does not have a checksum scheme for may simply report that no known scheme matched.

Understanding the answer

The output says…	In plain words
OK	The stored checksum matches the data — this block is untouched
STALE	The stored value differs from the recomputed one — the data was edited after the checksum was written
absent	The structure that would hold this checksum is missing from this file
no scheme(s) matched	This file's family is not covered by a known checksum scheme — nothing to compare

Schemes are checked per ECU family: Bosch ME7 (main, multipoint, rolling, multirange), IronFelix family profiles (VAG ME7.XX, M3.x, …), Siemens GS20/SMG2 and MS43, and Denso Subaru descriptor tables. Not every check runs on every file — only the schemes that fit the file's family.

For developers

The same detection is one method of openremap.api — same schemes, same OK/STALE result:

Way of using it	Where to look	Example
Terminal (CLI)	checksum — CLI	`openremap checksum my-file.bin`
Python code	checksum — API	`api.call("checksum", {"path": "my-file.bin"})`
Any language (JSON-RPC)	checksum — API	a request with `"method": "checksum"`

Where to go next

You want to…	Go to
See every option and the scheme-by-scheme reference	checksum — CLI
Call `checksum` from your own code	checksum — API
Run the six-check safety pass that includes checksums	`health`
First identify the file before checking it	`identify`