The Audi A4 B9 (2017–2023) is one of the most extensively documented Audi platforms in terms of coding options — years of VCDS and OBDeleven community contributions have mapped out virtually every available modification. This is the complete checklist of worthwhile coding changes, organized by what tool you need and what impact to expect.
ODIS-Required (Professional Service)
Matrix LED Full Activation
Applies to: Premium Plus and above with Matrix LED option
Impact: Adaptive high beam, permanent high-beam mode, dynamic cornering, full Euro headlight behavior
This is the most impactful single coding change available for the B9 A4. See our A4 B9 Matrix guide for full details.
Component Protection Clearance
Applies to: Cars with replaced modules
Impact: Enables proper function of replacement parts (HLCU, cluster, gateway)
VCDS or OBDeleven
Gauge Sweep on Startup
Module: Instrument cluster
Impact: ★★★☆☆ — Needles sweep to maximum on ignition start
Notes: Works on both analog instrument and Virtual Cockpit variants
Scandinavian DRL Mode
Module: Headlight control unit (HLCU)
Impact: ★★★★☆ — Position lights active alongside dipped beam, more distinctive light signature
Notes: Available on B9 and B9.5; specific byte changes depend on build
Coming Home / Leaving Home Duration
Module: HLCU
Impact: ★★★☆☆ — Extend illumination after lock/unlock up to 180 seconds
Notes: Duration, brightness, and enable/disable per ambient light condition all adjustable
Cornering Fog Light Activation
Module: HLCU
Impact: ★★★☆☆ — Fog light activates on turning side below speed threshold
Notes: Requires front fog light option to be present
Auto-Fold Mirrors on Lock
Module: Door/mirror module
Impact: ★★☆☆☆ — Mirrors fold on lock, unfold on unlock
Notes: Requires power-fold mirror option
Battery Coding (after replacement)
Module: BMS
Impact: ★★★★☆ — Essential after battery replacement to maintain correct BMS profile
Notes: Not cosmetic — affects battery life and charging behavior
Rain Closing (windows close when rain detected)
Module: Comfort module
Impact: ★★★☆☆ — Windows and sunroof close automatically when rain sensor activates
Notes: Requires sunroof and rain sensor options
Seatbelt Warning Adjustment
Module: Instrument cluster
Impact: ★★☆☆☆ — Adjust or disable seatbelt chime behavior
Notes: Regional regulations apply
Sport Display Modes (S and RS variants)
Module: Instrument cluster
Impact: ★★★☆☆ — Lap timer, G-force, performance data overlay in Virtual Cockpit
Notes: Primarily for S4 / RS4 variants
Ambient Lighting Zone Expansion
Module: Body/comfort electronics
Impact: ★★★☆☆ — Additional illuminated zones if hardware is present
Notes: Depends on specific build and ambient lighting package
The Recommended Coding Order
- Start with an ODIS session for Matrix activation (if equipped) — this is the high-impact, ODIS-only item
- In the same session, handle any component protection issues if present
- Post-session, use VCDS or OBDeleven for the remaining items at your leisure — these are all reversible and low-risk
Start with the biggest impact item: A4 B9 Matrix activation →