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2021 BMW LIN Bus Mirror Faults & Window Issues TSB

A manufacturer communication, TSB 10188944, addresses LIN bus faults in 2021 BMW 330i, Z4, X2, M340i, and 330e models. These faults can lead to exterior rearview mirror glass damage and issues with power window and mirror operation due to faulty mirror electronics.

ByAhmet Topcu — Founder & Editor-in-ChiefAutomated summary2021 BMW 330i
2021 BMW 330i — BMW 330i LIN bus fault
Editorial illustration generated for this article.
10188944LIN BUS FAULTS WITH EXTERIOR REARVIEW MIRROR GLASS DAMAGEexterior rearview mirror glass damagepower window operation issuesexterior mirror operation issuesfaulty exterior rearview mirror electronicsLIN bus short2021 BMW 330i2021 BMW Z42021 BMW X2
BMW 330e
2021
BMW M340i
2021
BMW X2
2021
BMW Z4
2021

BMW has issued Manufacturer Communication 10188944 to address concerns regarding LIN bus faults that can affect the exterior rearview mirrors and other vehicle functions. This communication highlights a specific issue where faulty mirror electronics can lead to significant problems, impacting various 2021 BMW models including the 330i, Z4, X2, M340i, and 330e. Owners experiencing issues related to their exterior mirrors or power windows should be aware of this bulletin.

Symptoms of LIN Bus Faults

Owners may notice several symptoms related to this issue. The primary concern is "LIN BUS FAULTS WITH EXTERIOR REARVIEW MIRROR GLASS DAMAGE," indicating visible damage to the mirror glass itself. Beyond physical damage, drivers might experience "functional errors in power window and exterior mirror operation." This means the power windows may not operate correctly, or the exterior mirrors might not adjust, fold, or heat as expected. These symptoms are key indicators of a potential underlying LIN bus fault.

Diagnosis and Cause

The root cause of these problems stems from "faulty exterior rearview mirror electronics." These electronics, when defective, can create a short circuit on the LIN bus. The LIN (Local Interconnect Network) bus is a serial communication system used in vehicles to control various components, especially in door modules and mirror assemblies. A short on this bus can disrupt communication, leading to the aforementioned mirror glass damage and functional errors. If you are experiencing a BMW 330i LIN bus fault, this is the likely culprit.

What Owners Should Know

This manufacturer communication, 10188944, serves to inform technicians about the potential for these LIN bus faults. While the document does not detail a specific repair procedure for owners, it indicates that diagnosis and resolution will involve addressing the faulty exterior rearview mirror electronics. If your 2021 BMW 330i, Z4, X2, M340i, or 330e exhibits symptoms such as damaged mirror glass or issues with power window and exterior mirror operation, it is recommended to contact your authorized BMW service center. They can diagnose the specific LIN bus fault and perform the necessary repairs to restore full functionality.

Source: NHTSA TSB 10188944.

What BMW 330i owners report

Counted from the records in our database across 16 model years.

818
Owner complaints
39
Recalls
863
Service bulletins
30
Crashes reported
38
Fires reported
36
Injuries reported

The 2021 model year

29 complaints, the 10th most of 16 model years on file. Owners reported 1 crash, 3 fires and 1 injury for this year, which also has 7 recalls on file.

Visibility, the system this article covers, accounts for 20 of 818 complaints (2%).

Complaints by model year

Model years with the most complaints for the BMW 330i
2001116
200245
200377
2004113
2006219
201742
201832
201941
202053
202129

Most-reported systems

  1. Air Bags — 246
  2. Exterior Lighting — 153
  3. Electrical System — 132
  4. Engine — 89
  5. Power Train — 44

Latest recalls for the 2021 model year

  • 26V056000 — Electrical System (Jan 2026)
  • 25V636000 — Electrical System (Sep 2025) — Park outside
  • 23V584000 — Electrical System (Aug 2023)
All 2021 recalls →

Recent owner reports about visibility

While I was driving down the highway, sunroof has exploded without any apparent reason. I really didn’t realize what had happened at first, all I heard was a loud bang which could’ve lead to distraction and cause an accident.

2021 BMW 330i owner, Feb 2023
Read owner complaints →

Complaints are owner reports filed with NHTSA. They are unverified, and counts depend on how many vehicles were sold, so they are not a failure rate.

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