Common problems

BMW 4 Series Common Problems

We grouped the top NHTSA owner-complaint categories across 9 BMW 4 Series model years, then counted how often each issue recurs. The result shows patterns worth inspecting without pretending every vehicle will have them.

Data updated April 2026

Owner complaints
579

9 model years

Top recurring issue
Electrical System

7 affected years

Crash reports
57

Owner-reported severity signal

Fire reports
17

66 injuries · 0 deaths

Pattern overview

Most reported BMW 4 Series problem categories

#1

Electrical System

89complaints represented

Appears among the leading issues for 7 model years; highest in 2018.

#2

Unknown Or Other

68complaints represented

Appears among the leading issues for 7 model years; highest in 2018.

#3

Air Bags

89complaints represented

Appears among the leading issues for 5 model years; highest in 2018.

#4

Engine

54complaints represented

Appears among the leading issues for 5 model years; highest in 2018.

#5

Power Train

26complaints represented

Appears among the leading issues for 5 model years; highest in 2019.

#6

Service Brakes

14complaints represented

Appears among the leading issues for 3 model years; highest in 2023.

#7

Exterior Lighting

5complaints represented

Appears among the leading issues for 2 model years; highest in 2019.

#8

Seat Belts

23complaints represented

Appears among the leading issues for 1 model year; highest in 2018.

#9

Engine And Engine Cooling

13complaints represented

Appears among the leading issues for 1 model year; highest in 2018.

#10

Electronic Stability Control (Esc)

5complaints represented

Appears among the leading issues for 1 model year; highest in 2023.

What owners reported

Issue summaries by BMW 4 Series model year

AIR BAGS

Owners of the 2018 BMW 4-Series frequently report issues with the passenger seat occupancy sensor, which often leads to a "Passenger restraint system malfunction" warning. This problem typically results in the deactivation of the passenger airbag, posing a significant safety risk. Complaints commonly involve vehicles with mileage under 40,000, and repairs for this issue can be costly, exceeding $2,000. Additionally, there are reports of airbags failing to deploy during accidents, leading to injuries. Used car buyers should be aware of these potential safety and financial implications.

Severity signals: 3 crash, 0 fire, 5 injury reports

ELECTRICAL SYSTEM

Owners of the 2018 BMW 4-Series frequently report electrical system issues, with common problems including passenger restraint system malfunctions, electrical call system failures, and intermittent electrical issues affecting various vehicle functions. Typical symptoms described involve warning lights, malfunctioning audio and navigation systems, and problems with the rear window defroster wiring, which in some cases lead to fires. Complaints often arise around the mid-range mileage of approximately 10,000 to 51,000 miles. Safety implications are significant, with reports of two crashes, two fires, and two injuries linked to these electrical problems. Potential buyers should be aware of these issues, as they may impact vehicle reliability and safety.

Severity signals: 2 crash, 2 fire, 2 injury reports

ENGINE

Owners of the 2018 BMW 4-Series frequently report issues with the engine related to coolant system failures, particularly involving the oil filter housing and coolant hoses. Common symptoms include overheating warnings, coolant leaks, and sudden engine shutdowns, often occurring around 50,000 to 65,000 miles. Several complaints also mention fires, with three incidents involving engine compartment fires and one report of an injury due to sudden speed reduction. Buyers should be aware of the potential for significant repair costs and the risk of engine damage if these issues are not addressed promptly.

Severity signals: 0 crash, 3 fire, 1 injury reports

ELECTRICAL SYSTEM

Owners of the 2020 BMW 4-Series frequently report issues related to an unresolved recall involving the electrical system, specifically the engine starter, which poses a fire risk when parked. Complaints often highlight the lack of available parts for the recall repair, leading to prolonged vehicle downtime and safety concerns. Some owners mention additional electrical problems, such as the Auto-Start feature failing to activate and software malfunctions impacting safety systems like Blind Spot Warning and Lane Departure Warning. A notable incident involves a vehicle starting and driving itself into a garage door, indicating potential for unexpected vehicle movement. These issues are reported across various mileage ranges, with some occurring around 17,000 miles, and present significant safety implications, including fire hazards and loss of vehicle control.

Severity signals: 1 crash, 0 fire, 0 injury reports

UNKNOWN OR OTHER

Owners of the 2019 BMW 4-Series frequently report issues related to exploding sunroofs, with multiple accounts of violent explosions sounding like gunshots and resulting in shattered glass inside the vehicle. Some owners also describe software update failures via the Over The Air (OTA) method, leading to additional costs for updates at dealerships. Additionally, there are complaints about a parked vehicle catching fire, which is linked to an active recall warning of potential fire risks. These issues present potential safety hazards, including risks of injury from glass and fire, and occur at various mileage ranges as no specific pattern emerges from the complaints.

Severity signals: 0 crash, 1 fire, 0 injury reports

ELECTRICAL SYSTEM

Owners of the 2021 BMW 4-Series frequently report issues related to the electrical system, with several complaints highlighting problems with the engine start/stop system, including difficulty starting the vehicle and failure to restart after stopping at lights. Some owners describe the vehicle's electrical components, like the remote starter and key fob, as malfunctioning, despite repeated battery replacements. Multiple reports involve a recall for an electrical system issue, with owners expressing frustration over the unavailability of repair parts. Notably, two complaints involve vehicle fires, occurring without prior warning signs or dashboard alerts, raising safety concerns. These issues are reported across varying mileage ranges, with some occurring as early as 200 miles.

Severity signals: 0 crash, 2 fire, 0 injury reports

UNKNOWN OR OTHER

Owners of the 2018 BMW 4-Series frequently report issues related to coolant and oil system leaks, often citing cracked plastic components as the cause, particularly around 60,000 to 70,000 miles. Symptoms include overheating and potential mixing of oil and coolant, which can lead to further engine damage. Several complaints also mention malfunctions in the vehicle's safety systems, such as ineffective rear cross-traffic alerts and inadequate lane departure warnings, which may compromise driving safety. Notably, there are reports of unintended acceleration and a fire incident, both of which resulted in injuries, highlighting significant safety concerns. Buyers should be aware of these recurring issues and their potential impact on vehicle reliability and safety.

Severity signals: 1 crash, 1 fire, 4 injury reports

SEAT BELTS

Owners of the 2018 BMW 4-Series frequently report issues with the passenger restraint system and seat belts. Common symptoms include a persistent "passenger restraint system malfunction" warning and false seat belt alerts, even when the seat is unoccupied or the seat belt is fastened. Some complaints mention the need for expensive repairs, such as sensor mat replacements, typically costing around $2000 to $2800. One report involves a crash where the passenger seat belt failed to lock properly, resulting in an injury. These issues often occur at varying mileages, with at least one case noted at 77,000 miles. Potential buyers should be aware of these reported malfunctions and the associated repair costs.

Severity signals: 1 crash, 0 fire, 2 injury reports

Pre-purchase inspection

What to check on a used BMW 4 Series

When problems are reported to begin

  • Service brakes failures — 0–100 miles on the 2024 model-year record
  • Service brakes failure — 900–6,470 miles on the 2023 model-year record
  • Electronic stability control issues — 6,470–40,000 miles on the 2023 model-year record
  • Power train failures — 1,000–69,000 miles on the 2022 model-year record
  • Electrical system failures — 59,000–70,000 miles on the 2022 model-year record
  • Motor mount failures — 43,000–60,000 miles on the 2021 model-year record
  • Brake component failures — 25,000–45,000 miles on the 2021 model-year record
  • Engine starter relay issues — 30,000–33,000 miles on the 2021 model-year record

Buyer red flags

  • Inspect wireless charging tray for overheating with metal phone cases
  • Test rear visibility with 'Theater Screen' deployed
  • Check rear window roller shade for visibility obstruction
  • Verify all optional features for potential safety hazards
  • Check for unresolved brake system recalls and verify brake function
  • Inspect sunroof for signs of stress or previous repairs
  • Test back over prevention system for timely alerts
  • Verify engine and electrical system warnings are absent during test drive

How to interpret the counts

Complaint totals are not failure rates

A popular or older model can accumulate more complaints simply because more vehicles exist and have spent longer on the road. The categories above aggregate the counts embedded in each model year's leading issues. Use recurrence across years and severity signals to decide what to inspect; use the VIN and a mechanical inspection to judge one car.

Source trail

Where this BMW 4 Series data comes from

VinExposed combines model-level research with the vehicle-specific history you get from a VIN. Reliability scores and complaint patterns come from Auto Reliability Index's BMW 4 Series research, which analyzes NHTSA records and independent repair data.

Recall counts describe a model year, not the repair status of one car. Confirm the exact VIN with the official NHTSA recall lookup and a vehicle-history report before buying.

Buyer questions

BMW 4 Series research FAQ

What is the most common BMW 4 Series problem?

Electrical System is the broadest recurring complaint category in the available model-year records, appearing among the top issues for 7 years with 89 complaints represented.

Which BMW 4 Series year has the most reported problems?

The 2018 has the largest electrical system count among the years where that category appears. Compare the full year record because a different year may lead on another problem category.

Do NHTSA complaints prove a BMW 4 Series has a defect?

No. Owner complaints are unverified reports and can be duplicated or influenced by sales volume and vehicle age. They are useful patterns to investigate alongside recalls, service records, inspection results and the exact VIN.

Check the actual car

Model research narrows the list. The VIN confirms the car.

Check title brands, accidents, odometer history, auction records and recall status for the specific BMW 4 Series you are considering.