Wiring or connector fault at the aero control module or its actuators (corrosion, chafing, loose pins); Low or unstable supply voltage or poor earth to the module; Seized or damaged actuator, motor or mechanism (ice, dirt, road debris, impact damage) overloading the module; Communication network fault preventing the module talking to other control units; Internal failure of the aero control module; Known software fault in the module that the manufacturer has corrected with an update.

B3A20

Active Aerodynamic Feature Control Module A.

Generic
Body
Generic code
Low severity

How this code is built

B: SystemBody
3: Defined bySAE, the same on every car
A: AreaBody area A
20: FaultThe specific fault in that area

What it means

B3A20 is a generic body code for the Active Aerodynamic Feature Control Module A. It points to a fault with the control unit that runs movable aero parts such as a rear spoiler, front air dam or active shutters, or with its circuit. The generic title does not say exactly what was detected (internal fault, supply, communication or output), so the precise trigger depends on the make and model.

Symptoms

Warning light or message about the active aero or spoiler system
Spoiler, air dam or shutters stuck up, stuck down or not moving when they should
Aero feature moving slowly, noisily or erratically
Other body or chassis modules reporting a lost communication fault with the aero module
Slightly higher fuel use or altered high-speed stability if a shutter or spoiler is stuck

Possible causes

Wiring or connector fault at the aero control module or its actuators (corrosion, chafing, loose pins)likely
Low or unstable supply voltage or poor earth to the modulelikely
Seized or damaged actuator, motor or mechanism (ice, dirt, road debris, impact damage) overloading the modulepossible
Communication network fault preventing the module talking to other control unitspossible
Internal failure of the aero control modulepossible
Known software fault in the module that the manufacturer has corrected with an updaterare

How to diagnose

Read all stored codes and freeze frame data, noting any related network, voltage or actuator codes, then check whether B3A20 is current or historic
Visually inspect the aero feature and its mechanism for damage, debris, ice or obstruction, and operate it by hand where safe to check for binding
Inspect the module and actuator connectors and wiring for water ingress, corrosion, chafing and bent or pushed-back pins
Check battery condition and charging voltage, and test the power and earth feeds at the module against the wiring diagram
Check for network communication faults and confirm the module is responding on the bus
Use a bidirectional scan tool function, if the model supports it, to command the aero feature and watch whether it moves and what current or position feedback the module reports
Look up manufacturer technical information for the specific make and model, as the module location and test procedure vary
Clear the code after repair and road test to confirm it does not return

How to fix

Repair or replace damaged wiring, terminals or connectors, and treat any corrosion
Correct supply or earth problems, and restore battery and charging system health
Free, repair or replace a jammed or damaged actuator or aero mechanism
Repair the underlying network fault if communication is the cause
Replace the aero control module if it is confirmed faulty, coding or programming it to the vehicle as the manufacturer requires
Apply a manufacturer software update for the module only where one is published for this fault

Can I keep driving?

Low severity

The car is normally fine to drive and the fault should be booked in. If the spoiler or other aero part is stuck deployed, loose or damaged, limit speed and have it checked soon to avoid it detaching or affecting stability.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.