B3A21

Active Aerodynamic Feature Control Module B

Severity

⚠️ Medium

Can you drive?

Limited driving only, diagnose soon

Approx. repair cost

$56–278 (est.)

Symptoms

Error message on the dashboard
Inability to adjust active aerodynamic elements
Fixing spoilers/air intakes in one position
Reduced stability at high speeds

Causes

Problems with module wiring harness
Control solenoid valve malfunction
Mechanical jamming of elements
Module software failure
Contact corrosion

How to Fix

Diagnostics of the module electrical circuit
Checking mechanical elements for free movement
Testing the operation of solenoid valves
Resetting the error and checking for recurrence
Reflashing or replacing the module if necessary

Related codes

B3A20 B3A22 U0121