When your 2020 BMW 5 Series displays the P0305 code, the diagnostic approach depends on your engine. The G30 2020 5 Series offers inline-four, inline-six, and V8 options. P0305 is valid on six-cylinder and V8 models but anomalous on the four-cylinder 530i.
2020 5 Series Engine Options
The 2020 5 Series offers the 2.0L B48 I-4 (248 hp in 530i), 3.0L B58 I-6 (335 hp in 540i), and 4.4L N63 V8 (523 hp in M550i). P0305 is valid on I-6 and V8 models.
Diagnosis
At 2020 mileage levels, spark plug wear is possible. Ignition coils can fail. Carbon buildup on direct-injection intake valves is common. Check maintenance history.
Four-Cylinder
530i has only cylinders 1-4. P0305 is anomalous.