# B1252 on the 2026 Mazda Mazda3

The bulletins listed name this code in NHTSA's summary, or are about the same components. A bulletin or a recall listed here may apply to the model year. None of it is a diagnosis.

This code is specific to a manufacturer and is not described here.

## Bulletins for this model year that name B1252

- [11037632](https://open.wenmarpro.com/bulletins/11037632), 2026-10-01: DESCRIPTION Some customers may experience a message "TCU Malfunction. Have the Vehicle Inspected" in the instrument cluster. Additional symptoms that may occur: Connected Vehicle One Time Passcode \(OTP\) may fail. Connected Vehicle Remote functions may fail. The following DTC's may be stored: B1252:87\-8B:TCU \- COMMUNICATION ERROR WITH CONNECTIVITY MASTER UNIT \(CMU\) U0198:00\-03:CMU \- COMMUNICATION ERROR WITH EMERGENCY CALL UNIT/TELEMATICS COMMUNICATION UNIT REPAIR PROCEDURE 1. Verify the concern. 2. Check if any of the following DTCs are stored: B1252:87\-8B:TCU \- COMMUNICATION ERROR WITH CONNECTIVITY MASTER UNIT \(CMU\) U0198:00\-03:CMU \- COMMUNICATION ERROR WITH EMERGENCY CALL UNIT/TELEMATICS COMMUNICATION UNIT Are the following DTCs stored? YES: Proceed to next step. NO: This service information does not apply. Continue troubleshooting using MGSS.
- [11037017](https://open.wenmarpro.com/bulletins/11037017), 2026-09-04: This Service Alert supersedes the previously issued SA\(s\) listed below. The changes are noted in Red. SA\-012/26 04/17/26, 03/04/26 and 02/26/2026 DESCRIPTION Some customers may experience a message "TCU Malfunction. Have the Vehicle Inspected" in the instrument cluster. Additional symptoms that may occur: Connected Vehicle One Time Passcode \(OTP\) may fail. Connected Vehicle Remote functions may fail. The following DTC's may be stored: B1252:87\-8B:TCU \- COMMUNICATION ERROR WITH CONNECTIVITY MASTER UNIT \(CMU\) U0198:00\-03:CMU \- COMMUNICATION ERROR WITH EMERGENCY CALL UNIT/TELEMATICS COMMUNICATION UNIT REPAIR PROCEDURE 1. Verify the concern. 2. Check if any of the following DTCs are stored: B1252:87\-8B:TCU \- COMMUNICATION ERROR WITH CONNECTIVITY MASTER UNIT \(CMU\) U0198:00\-03:CMU \- COMMUNICATION ERROR WITH EMERGENCY CALL UNIT/TELEMATICS COMMUNICATION UNIT
- [11032015](https://open.wenmarpro.com/bulletins/11032015), 2026-05-04: Some customers may experience a message "TCU Malfunction. Have the Vehicle Inspected" in the instrument cluster. Additional symptoms that may occur: Connected Vehicle One Time Passcode \(OTP\) may fail. • Connected Vehicle Remote functions may fail. • The following DTC's may be stored: B1252:87\-8B:TCU \- COMMUNICATION ERROR WITH CONNECTIVITY MASTER UNIT \(CMU\) • U0198:00\-03:CMU \- COMMUNICATION ERROR WITH EMERGENCY CALL UNIT/TELEMATICS COMMUNICATION UNIT REPAIR PROCEDURE 1. Verify the concern. 2. Check if any of the following DTCs are stored: B1252:87\-8B:TCU \- COMMUNICATION ERROR WITH CONNECTIVITY MASTER UNIT \(CMU\) • U0198:00\-03:CMU \- COMMUNICATION ERROR WITH EMERGENCY CALL UNIT/TELEMATICS COMMUNICATION UNIT Are the following DTCs stored? YES: Proceed to next step. • NO: This service information does not apply. Continue troubleshooting using MGSS. • 3. Check for electrical devices in the vehicle such as a device connected to USB hub, Dash Cam, Insurance Device, FasTrak........ect. Are there any customer electrical devices in the vehicle? YES: Document customer device used, then go to the next step. • NO: Go to the next step. • 4. Clear the DTC's
- [11030631](https://open.wenmarpro.com/bulletins/11030631), 2026-04-02: This Service Alert supersedes the previously issued SA\(s\) listed below. The changes are noted in Red. SA\-012/26 02/26/2026 DESCRIPTION Some customers may experience a message "TCU Malfunction. Have the Vehicle Inspected" in the instrument cluster. Additional symptoms that may occur: Connected Vehicle One Time Passcode \(OTP\) may fail. Connected Vehicle Remote functions may fail. The following DTC's may be stored: B1252:87\-8B:TCU \- COMMUNICATION ERROR WITH CONNECTIVITY MASTER UNIT \(CMU\) U0198:00\-03:CMU \- COMMUNICATION ERROR WITH EMERGENCY CALL UNIT/TELEMATICS COMMUNICATION UNIT REPAIR PROCEDURE 1. Verify the concern. 2. Check if any of the following DTCs are stored: B1252:87\-8B:TCU \- COMMUNICATION ERROR WITH CONNECTIVITY MASTER UNIT \(CMU\) U0198:00\-03:CMU \- COMMUNICATION ERROR WITH EMERGENCY CALL UNIT/TELEMATICS COMMUNICATION UNIT Are the following DTCs stored? YES: Proceed to next step. NO: This service information does not apply. Continue troubleshooting using MGSS. 3. Check for electrical devices in the vehicle such as a device connected to USB hub, Dash Cam, Insurance Device, FasTrak........ect. Are there any customer electrical devices in the vehicle? YES: Document customer device used, then go to the next step. NO: Go to the next step. 4. Check for a Navi SD Card. Is the vehicle equipped with a Navi SD Card? YES: Replace the Navi SD Card. NO: Go to next step. 5. Complete the Dealer Connected Vehicle Questionnaire. 6. Collect CMU log data. Go to Infotainment/TCU \-\-\> Collecting CMU Log Data \-\-\> CMU Log Data Retrieval Instructions 7. Collect TCU log data. Go to Infotainment/TCU \-\-\> TCU Log Data Retrieval Instructions \-\-\> CMU Log Data Retrieval Instructions 8. Contact Hotline for additional assistance. 9. Release the vehicle to the customer. NOTE: This concern is currently under investigation
- [11029531](https://open.wenmarpro.com/bulletins/11029531), 2026-03-04: This Service Alert supersedes the previously issued SA\(s\) listed below. The changes are noted in Red. SA\-060/25 12/16/25 Some customers may experience a message "TCU Malfunction. Have the Vehicle Inspected" in the instrument cluster. Additional symptoms that may occur: Connected Vehicle One Time Passcode \(OTP\) may fail. Connected Vehicle Remote functions may fail. The following DTC's may be stored: B1252:87\-8B:TCU \- COMMUNICATION ERROR WITH CONNECTIVITY MASTER UNIT \(CMU\) U0198:00\-03:CMU \- COMMUNICATION ERROR WITH EMERGENCY CALL UNIT/TELEMATICS COMMUNICATION UNIT
- [11026913](https://open.wenmarpro.com/bulletins/11026913), 2026-01-03: Some customers may experience a message "TCU Malfunction. Have the Vehicle Inspected" in the instrument cluster. The following DTC's may be stored: B1252:87\-8B:TCU \- COMMUNICATION ERROR WITH CONNECTIVITY MASTER UNIT \(CMU\) • U0198:00\-03:CMU \- COMMUNICATION ERROR WITH EMERGENCY CALL UNIT/TELEMATICS COMMUNICATION UNIT