USDM 2023 WRX ‘B’ ROM Support


We recently released Accessport tuning support for the 2023 Subaru WRX 6MT along with a host of bolt-on upgrades that make up our Stage 2 Power Package.  Immediately after release, we received reports of users encountering an “Unknown ROM” error when attempting to install the Accessport onto their 2023 WRX.  This was due to an ECU update from Subaru, which our COBB development cars did not have as they were early deliveries.  An important note about this type of update from Subaru – we did not observe any changes to calibration data compared the initially supported “A” ROM, but Subaru often pushes background logic updates that may impact things like DTC triggers.  For that reason, we have updated our available Off The Shelf Maps to be based on the newer logic, removing compatibility of initial maps, and deprecating the “A” ROM in Accesstuner Pro.

Today, we are excited to announce that support for vehicles with the “B ROM” is now available by way of a an Accessport firmware update, new Off The Shelf Maps, and new ECU type in Accesstuner Pro.

Accessport Firmware Update

If you already have a SUB-006 Accessport for you 2023 WRX and will be using a COBB OTS Map, you simply need to update your Accessport’s firmware using Accessport Manager on your computer.

Updating Your Accessport

Deprecated ECU Type & OTS Maps

In practice, we do our best to base our software and Off The Shelf Maps on the most recent factory code.  Even when there are not calibration changes that impact the engine’s performance and output, there may be background changes to the operating system that improve things like DTC triggers or how the ECU interacts with other modules in the vehicle.  For that reason, we have moved all support for 2023 WRXs to the updated ‘B’ ROM and removed support for the ‘A’ ROM.  Beyond that, a potential bug was discovered during additional testing in which the vehicle’s engine may stumble when using any non-COBB data logger or live gauge viewing device while any map based upon the ‘A’ ROM is flashed to the ECU, including both COBB OTS and third-party maps.

  • ‘A’ ROM COBB OTS Maps can not be flashed by updated AP Firmware
    • Any v120 or v121 OTS map
  • Custom tunes based on the ‘A’ ROM will need to be imported into the ‘B’ ECU in Accesstuner Pro before they can be flashed using new Accessport firmware

New Off The Shelf Maps

As we mentioned earlier, there are no calibration data differences between the “A” and “B” variant ROMs, at least within the tables exposed as part of our product offering.  These new Off The Shelf Maps are simply resaved in an ECU type that is based upon the “B” ROM in order t pick up any background logic changes implemented by Subaru.  Power output is unchanged.  To reflect this update, OTS Maps will be noted as version v130.

The following Maps are packaged in Accessport Firmware

  • Stage0 v130.ptm

  • Stage1 91 v130.ptm

  • Stage1 93 v130.ptm

  • Stage1 Economy Mode v130.ptm

  • Vehicle Anti-Theft Mode v130.ptm

The following Maps are not packaged in Accessport firmware but are available for download from the maps section of our website:

  • Stage2 91 v131.ptm

  • Stage2 93 v131.ptm

For more information about COBB Off The Shelf Maps, visit our Map Notes Page.

Additional Modifications

Looking for more than just increased power output for your 2023 Subaru WRX?  We already offer a host of parts to improve shifter feel, reduce drivetrain slop, and dress-up the engine bay.

COBB Edition Wheels by Titan7

2 responses to “USDM 2023 WRX ‘B’ ROM Support”

    • There are not likely any specific calibration changes that would lead to the perceived difference in performance. It’s almost certainly something to do with learned values, fuel trims, etc, after flashing the ECU.


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