FORScan AS-Built Backup and Restore (Mazda)

AS-Built data is the configuration stored in each vehicle module — RBCM, FBCM, SSU, IC, and others. Reading and saving it before you make any FORScan change is the single most important step in the whole process. With a backup, every mistake is reversible. Without one, you are guessing at original values.

Export before any dealer visit

Save your AS-Built data before any dealer service. Dealers reset or overwrite module configuration during firmware updates and recall work, and they will not restore your custom values. A backup is the only way to know what the module held before they touched it.

What AS-Built data is

Each module stores its configuration as hexadecimal bytes organized into blocks. Those bytes control:

• Feature enablement (door lock behavior, DRL mode, i-Stop default)
• Hardware configuration (sensor presence flags, peripheral settings)
• Regional calibration (market-specific defaults)
• Checksums (integrity verification bytes appended to each block)

“AS-Built” is the automotive term for the configuration as the vehicle left the factory.

Backup procedure

Prerequisites

• FORScan installed with an extended license
• A compatible adapter connected in the correct CAN mode — MS-CAN for body modules
• Ignition in the ON/ACC position (engine off is fine)

Step by step

1. Connect and scan. Open FORScan, click Connect, and run a module scan. Verify RBCM, FBCM, SSU, and IC appear in the module list.

2. Read AS-Built data for each module. Select a module (for example RBCM at address 0x7B7), open the AS-Built Data tab, and click Read. Wait for all blocks to populate.

3. Save to file. Click Save to file / Export. Name it descriptively, like RBCM_7B7_stock_YYYY-MM-DD.abt, and put it somewhere you will not lose it (not the car’s USB drive).

4. Repeat for every module you plan to modify:

   • RBCM (0x7B7) — door locks, lighting
   • FBCM (0x726) — DRL, ESS, wipers
   • SSU (0x731) — i-Stop, keyless
   • IC (0x720) — cluster display, cruise type

5. Back up everything, not just the modules you will touch. A full baseline costs a few extra minutes and protects you against accidental writes to the wrong module.

Where to keep backups

Store copies in more than one place — on your computer in a labeled folder, and in cloud storage (Drive, iCloud, Dropbox). Do not keep your only copy on a USB drive that lives in the car.

Verify the backup

A backup you can’t load isn’t a backup. Confirm it works before you change anything:

1. Close the AS-Built view, then re-open the module.
2. Click Load from file and select your backup.
3. Compare the loaded values against what the module currently reports. They should match exactly.

Restore from backup

When a change causes problems and you need to revert:

1. Connect the adapter and scan modules.
2. Select the module to restore and open the AS-Built Data tab.
3. Click Load from file and select your backup.
4. Click Write to send the backup data to the module.
5. Confirm the write succeeded; the backup already contains the correct original checksums.
6. Cycle the ignition if the module needs it (see below).

Notes on restoration

• A write overwrites all data in those blocks. If you made several changes across multiple sessions, restoring an old backup reverts every one of them — not just the last.
• Some modules need an ignition cycle (key off, wait 30 seconds, key on) before the restored configuration takes effect.

Compare what changed

FORScan can diff current module data against a saved file:

1. Read the current AS-Built from the module.
2. Load a backup file.
3. FORScan highlights the bytes that differ.

That diff tells you exactly which bits changed — useful for confirming you only touched what you intended, for spotting unexpected modifications (a dealer visit is a common culprit), and for documenting your changes for next time.

Checksums in backups

Backup files store the checksum bytes as they were at backup time, so a straight restore is safe. The checksum only matters when you write modified data:

1. Use the Mazda SkyActiv OBD-II checksum spreadsheet (see the FORScan overview for where to find it).
2. Enter the modified hex values.
3. The spreadsheet returns the correct new checksum.
4. Update the checksum byte before writing.

Never write modified data without recalculating the checksum. The module will either reject the write or store corrupted data.

Recovery from a bad write

Scenario	Recovery
Write accepted but behavior is wrong	Restore from backup
Write rejected (checksum error)	Data unchanged; recalculate checksum and retry
Dashboard warning lights after write	Restore from backup, then clear DTCs
Module unresponsive after write	Ignition cycle; if still dead, the dealer may need to reflash
Wrote to the wrong module	Restore that module from backup

In practice, bad writes to body control modules (RBCM, FBCM, SSU) are almost always recoverable by restoring the backup. These modules have no write-protection that permanently locks you out.

Community AS-Built values

If you have no backup and need stock values:

Resource	Content
Mazda3Revolution AS-Built thread	Stock values for many Mazda3 and CX-5 configurations
FORScan forum, Mazda section	Module-specific stock value discussions
OHP Tools AS-Built data list	Documented stock values by model and trim

These give you a baseline, but they may not match your exact trim, region, or options. Your own backup is always the more reliable source.

Related pages

• FORScan overview — what FORScan can change, CAN bus architecture, safety boundaries
• Adapter buying guide — which OBD-II adapters support MS-CAN
• ND MX-5 FORScan — vehicle-specific changes for the MX-5
• CX-5 FORScan — vehicle-specific changes for the CX-5