BMW 4 Series (G22/G23/G26) Common Problems & Reliability
The second-generation 4 Series (G22/G23/G26) caused a major stir upon its launch due to its bold, vertically oriented kidney grilles, designed to distinguish it sharply from the conservative 3 Series. Beneath the controversial styling lies a highly capable and refined grand tourer, offering exceptional cruising ability and improved chassis rigidity over its predecessor. Mechanically, the G22 generation benefits heavily from the mature B-series powertrains, with the B48 four-cylinder and B58 six-cylinder petrol engines proving remarkably reliable and efficient. Mild-hybrid (MHEV) technology was introduced across much of the range, improving low-end response and efficiency, though the 48V system adds complexity to the electrical architecture. Build quality is a significant step up, with an interior practically lifted straight from the more expensive 8 Series. However, UK buyers should be aware that the car's considerable width and limited rearward visibility make parking sensors and surround-view cameras almost mandatory. Also, ensure the advanced driver-assistance systems (ADAS) are fully functional, as radar and camera calibration can be costly if misaligned.
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Detailed fault breakdown, symptoms, and estimated repair bills by production year.
Most Common BMW 4 Series (G22/G23/G26) Faults & Repair Costs
Radar Sensor Misalignment
The front radar sensor located in the large kidney grille is vulnerable to even minor "nudges", which can knock it out of alignment and disable the cruise control and safety systems.
"Driver Assistance Restricted" warning on dash, Active Cruise Control refusing to engage, Emergency braking system warnings
- Inspect the radar sensor for any visible cracks or impact marks
- Ask for a diagnostic report if any assistance warnings are present
- Check if the sensor bracket is loose
Coolant Loss (B58 Engine)
The M440i can suffer from slow coolant loss, often from the expansion tank cap or a minor weep from the water pump or turbo cooling lines.
Low coolant warning on the iDrive, Sweet smell of coolant after a spirited drive, Dried white residue around the expansion tank cap
- Check the coolant level when the engine is stone cold
- Inspect the expansion tank for hairline cracks
- Look for any signs of blue or green residue on the front of the engine
Active Grille Shutter Motor Failure
The motorised flaps behind the front grilles can fail to open or close correctly, throwing an engine management light and affecting aerodynamics.
Check Engine Light (EML) with air flap codes, Flaps stuck in one position, Fan running more than usual
- Verify the shutters move during the vehicle's startup sequence
- Check for any debris (leaves/stones) lodged in the mechanism
Buying a used BMW 4 Series (G22/G23/G26)? Always check for hidden finance and write-off history.
Mechanical problems are only half the battle. Over 1 in 3 UK used cars checked have unpaid finance or accident write-off records that could cause you to lose the car or thousands in value.