DTC B2242 “UART COMMUNICATION” – 2018 Subaru Legacy & Outback

NHTSA ID Number: 10166887

Manufacturer Communication Number: 15-225-18R


This Service Information bulletin provides a procedure to use when diagnosing the infotainment system, a DTC B2242- “UART COMMUNICATION” is stored in memory. UART communication occurs between the infotainment head unit (H/U) and the Auto HVAC system control panel.


2 Affected Products





This Service Information bulletin provides a procedure to use when diagnosing the infotainment system, a DTC B2242- “UART COMMUNICATION” is stored in memory.  UART communication occurs between the infotainment head unit (H/U) and the Auto HVAC system control panel.



This bulletin applies to the following Harman head units:

  • 86431AL61A “Base” w/ 6.5” display screen
  • 86431AL65A / 66A “Mid” (Display Audi w/ CD but w/o Navigation) w/ 8” display screen
  • 86471AL65A / 66A “High” (w/ CD and Navigation) w/ 8” display screen



REMINDER:  Customer satisfaction and retention starts with performing quality repairs.

Always refer to the applicable Service Manual and review the full requirements of the repair being performed.  The Service Manual procedures contain information critical to performing an effective repair the first time and every time.  This includes but is not limited to: important SAFETY precautions, proper inspection criteria, necessary special tools, required processes and related onetime-use parts needed for a complete and lasting repair.

NOTE:  The “Base” H/U does not support UART communication.  Therefore, if a B2242 DTC appears in memory, STOP as it is not a fault.  Clear the memory and do not attempt any further diagnostics.


For “Mid” and “High” systems, perform the following diagnostic procedure to confirm UART communication is functioning properly:

Step 1: Make sure the Auto AC system is set to OFF.


Step 2: Press the Talk switch (1) on the steering wheel satellite switch to initiate the Voice Recognition feature.


Step 3: Confirm the Popular Commands screen is displayed and that the list is shown in English.

  • If the list is not shown in English, access “General Settings” after pressing “Settings” on the Home screen, scroll down the list to “System Language” and select the applicable “English” option.


Step 4: In a normal voice, say “Auto AC on” into the microphone located in center of the overhead console.


  • If the system responds with “OK Turning Auto AC on”, proceed to Step 5.
  • If any other response is provided or a command is requested again, repeat Step 4.
  • If the system still does not respond with “OK Turning Auto AC on” and the command list has disappeared from the screen, try again starting with Step 2.


Step 5: Confirm the Auto AC system is now ON.

  • If the system is set to “AUTO ON”, UART communication is operating normally and testing is complete.
  • If the system responds with “Cancelling”, re-confirm the vehicle is equipped with either a “Mid” or “High” level H/U. If equipped with a “Mid” or “High” level H/U and the system responds with “Cancelling”, inspect the harness as outlined in the applicable Service Manual diagnostic procedure for DTC B2242.

NUMBER: 15-225-18R
DATE: 08/08/18
DATE: 10/02/19



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Last update on 2019-11-13 / Affiliate links / Images from Amazon Product Advertising API

Last update on 2019-11-13 / Affiliate links / Images from Amazon Product Advertising API

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