A significant reliability step up from the N20, with a more robust timing chain and fewer of the older engine's known weak points.
The B46 is a 2.0-litre turbocharged four-cylinder that replaced the N20 across BMW's mid-size range from the mid-2010s.
Direct injection still leads to gradual carbon accumulation, though generally less severe than on the N20.
The B46's timing chain is significantly more robust than the N20's, but wear can still occur on very high-mileage examples.
A light rattle from the wastegate actuator can develop under partial throttle.
The electric water pump is a service item that can fail over time.
Routine servicing is generally enough to keep the B46 trouble-free — one of BMW's more dependable modern four-cylinders.
Full BMW-specific diagnostic scan to identify the exact source of the issue rather than guessing.
Checking known leak points, wear items and service history against the B46's specific weak spots.
Confirming any rattle, misfire, or rough-running symptoms under real driving conditions.
Carbon build-up on the intake valves is the most commonly seen B46 issue — major faults are uncommon compared to the N20 it replaced.
The B46 was used in 3 Series (F30/G20), 5 Series (F10/G30), X1/X3 (F48/G01) and 2 Series (F22).
Considerably more reliable than the N20, with fewer known weak points and a more durable timing chain design.
Book a diagnostic with our BMW-trained technicians in Merrimu — serving Melton, Bacchus Marsh, and Melbourne's western suburbs.