A4buyer's guide

The B9 A4 is one of the best-built premium sedans of the last decade — when serviced. Skip the timing chain or wet-belt service window, ignore an AdBlue warning, neglect the S tronic fluid, and this car gets very expensive very fast. This guide walks you through the field checks before you put down a deposit.

This guide covers ten documented issues: timing chain stretch and wet-belt service risk (EA888 / EA211), S tronic and torque-converter automatic judder, AdBlue, DPF and EGR emissions faults, coolant leaks and water-pump failure, MMI infotainment and software electrical faults, suspension knocks and uneven tyre wear, brake corrosion and electronic parking brake faults, panoramic roof and boot water leaks, ADAS radar and camera calibration after windshield work, and the full recall and campaign checklist. Each fault has a field check and a real repair-cost range.

A documented B9 A4 will hold its value and outlast most of its competitors. An undocumented one is the most common premium-sedan trap on the used market. This guide makes the difference visible.