B1252
0 owner reports and 103 manufacturer filings across 18 model years from Ford, Mazda.
Where B1252 shows up
Source: NHTSA manufacturer communications and complaints| Model year | Filed under | Bulletins | Owner reports |
|---|---|---|---|
| 2026 Mazda CX-50 | Electrical System | 10 | — |
| 2025 Mazda CX-50 | Unknown Or Other | 10 | — |
| 2026 Mazda CX-70 | Unknown Or Other | 9 | — |
| 2025 Mazda CX-70 | Unknown Or Other | 9 | — |
| 2026 Mazda CX-90 | Unknown Or Other | 9 | — |
| 2025 Mazda CX-90 | Electrical System | 9 | — |
| 2024 Mazda CX-90 | Unknown Or Other | 8 | — |
| 2026 Mazda CX-30 | Electrical System | 5 | — |
| 2025 Mazda CX-30 | Electrical System | 5 | — |
| 2026 Mazda Mazda3 | Electrical System | 5 | — |
| 2025 Mazda Mazda3 | Electrical System | 5 | — |
| 2024 Mazda CX-30 | Unknown Or Other | 4 | — |
| 2024 Mazda Mazda3 | Unknown Or Other | 4 | — |
| 2020 Mazda CX-30 | Electrical System | 3 | — |
| 2020 Mazda Mazda3 | Electrical System | 3 | — |
| 2019 Mazda Mazda3 | Electrical System | 3 | — |
| 2017 Ford Mustang | Equipment | 1 | — |
| 2016 Ford Mustang | Equipment | 1 | — |
A model year appears here because the code is named in its record, not because every one of these vehicles sets it. Counts are mentions in the federal files, not failure rates — nobody publishes the denominator.
What it gets filed under
Manufacturer filings that name it
Source: NHTSA manufacturer communicationsService bulletins and campaigns whose filed summary names B1252. Quoting the document number at a service desk is often the fastest route to a diagnosis someone has already written down.
- SA-012-26b2026-04-18 · Electrical System
- 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 W
- SA-012-26a2026-03-04 · Electrical System
- 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'
- SA-012-262026-02-27 · Electrical System
- 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
- SA-060-252025-12-17 · Unknown Or Other
- 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
- SA-0290-20c2020-06-05 · Equipment — Electrical
- Some customers may experience a "IN-VEHICLE NETWORK MALFUNCTION" warning message in the instrument cluster with one or more of the following DTC's stored: ï· B119F:01 TCU - Tel antenna No. 1 malfunction ï· B1252:87 TCU - Communication error with connectivity master unit (CMU) ï· U0156:00 VCM - communication error with connectivity master unit (CMU) ï· U0156:00 BCM - Communicatio
- SA-029-20a2020-04-08 · Equipment Adaptive/Mobility
- Some customers may experience a "IN-VEHICLE NETWORK MALFUNCTION" warning message in the instrument cluster with one or more of the following DTC's stored: ï· B119F:01 TCU - Tel antenna No. 1 malfunction ï· B1252:87 TCU - Communication error with connectivity master unit (CMU) ï· U0156:00 VCM - Communication error with connectivity master unit (CMU) ï· U0156:00 BCM - Communication
What B1252 means
Source: SAE J2012 / OBD-IIB1252 is a manufacturer-specific code: the second character is a 1, which under the OBD-II standard hands the definition to whoever built the vehicle. The same code can mean one thing on a Ford and something unrelated on a Hyundai. Any site that prints a single definition for it is guessing.
A stored code names the test that failed, never the part that caused it. It is the starting point of a diagnosis, not its conclusion — the same code has several possible causes and the cheap one is not always right.
Common questions about B1252
Source: NHTSA files and the OBD-II standardWhy does this page not define B1252?
Because it cannot be defined honestly. The second character of a trouble code says who owns its meaning, and a 1 or a 3 hands that to the manufacturer. Sites that print one definition for a manufacturer-specific code are showing you one automaker's meaning and hoping it is yours.
Can I keep driving with B1252 stored?
Nobody can answer that from the code alone, and a site that does is guessing. A steady light generally means the fault was logged and the vehicle is in a reduced-risk mode; a flashing light means stop soon, because a misfiring engine can destroy a catalytic converter in minutes. The safe read of this page is the mileage and the components, not permission.
Does a code mean the car is recalled?
No. Recalls are filed by campaign and matched by VIN, and none of them are triggered by a scan tool. If you want to know whether an open recall applies to one specific vehicle, check the VIN at nhtsa.gov/recalls — that is the only source that settles it.
Why do the counts here differ from other sites?
Because these are not estimates. Every number on this page is a count of documents in NHTSA's own files: manufacturer communications that name the code in their filed summary, and owner complaints that name it in the narrative. We do not model, weight or extrapolate them.
Will clearing the code fix it?
Clearing turns the light off and erases the freeze-frame data a technician would have used to work out what happened. If the condition is still there the code returns, usually within a few drive cycles, and the diagnosis now starts from less information than before.