A steady ABS warning light on an Audi A4 B9 often points to a wheel speed sensor, wiring, or encoder ring issue.
Here’s what to check first and whether it’s safe to keep driving.
Why your A4 B9’s ABS light is staying on
On the B9 A4 (2016+), a continuously lit ABS lamp usually means the ABS control module has logged a fault and disabled ABS and stability control. The most common culprit is a wheel speed sensor or its magnetic encoder ring, especially after brake work, wheel bearing replacement, or a winter of road salt. But the light is a symptom, not a diagnosis: the module needs to be scanned for codes before you replace anything.
