Caterpillar .FLS Checksum Correction
Checksum correction for edited Caterpillar .FLS flash files. Flat rate per file, returned ready to flash with Cat ET.
How this service is delivered: after checkout, send us the file you edited. Use the contact form (up to 25 MB per file) or just reply to your receipt — and send the original read too, if you still have it. Nothing connects to your truck: the file comes back ready to use, usually within one business day, with everything you edited left exactly as you edited it.
Questions before you order? Ask on WhatsApp
Caterpillar .FLS checksum correction
Caterpillar ships its flash files as .FLS, a text-based S-record format rather than a plain binary dump. That means an edit has to survive twice over: the record structure itself has to stay valid, and the checks inside the file have to match the new contents. Get either wrong and Cat ET will not touch it. We fix both and give you a file that flashes.
When to order
- Cat ET reports the .FLS as invalid, corrupt, or refuses to load it after an edit.
- You converted a .FLS to binary, worked on it, and need it packed back correctly.
- A file was edited in a text editor and the record lines no longer add up.
Important: send the original as well
For Caterpillar we really do need both files — the edited one and the untouched original .FLS. Some of what has to be recalculated can only be derived from the original file; without it the job either cannot be finished or turns into guesswork, and we do not guess with flash files. If the original is genuinely lost, tell us before you order and we will say whether it is still doable.
What to send
- The edited .FLS.
- The original .FLS — required, see above.
- The part number the file belongs to, if you have it.
How the order runs
- Order the service — one order per file pair.
- Send both files through the contact form (up to 25 MB each) or by reply to your receipt.
- We correct the file and send it back in the same format you sent it, usually within one business day.
Asked often
Do you return a .FLS or a binary? A .FLS — the same format you sent, ready for the tool you already use.
Are the C-series engines covered? That is what this service is built around. If you have something unusual, ask before paying.
Is my tune modified? Never. Only what the file needs to be valid is touched.
More services: checksum and decryption, family by family. We work on tuning, calibration and file repair only — we do not remove or disable emissions equipment.
Specifications
| Engine platform | Caterpillar |
| Service type | Checksum Service |
| Method | You send the file, we send it back — nothing connects to your truck |
| Required from you | The edited file, and the original read if you still have it |
| Price | $200.00 USD, one file |
| Reference | vd-cks-cat-fls |
Four steps, start to finish
Order the right line
Pick the family that matches your file and pay. One order per file — batches are welcome, one line each.
Send the file
Reply to the receipt or use the contact form. Send the original read too if you still have it: it is not required, but it halves the guesswork.
We do the work
A technician confirms which family and map area the file belongs to, then corrects the checksums — or decrypts the file, if that is what you ordered.
You get it back
Back to the same email address, usually within one business day, done and ready to use.
- One file, one price — no subscription, no hourly billing.
- Nothing is connected to your truck: this is file work from start to finish.
- Only what has to change changes — your edits come back exactly as you made them.
No reviews on this one yet. If we have done this job for you, a couple of lines helps the next person decide.
