B3A28

Code

Generic B — Body

Active Aerodynamic Feature Control Module B Power Mode Circuit High Voltage

Brand: Generic

Type: B — Body

Views: UK: 16 EN: 25 RU: 23

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Page language: EN

Short to battery (B+) on the module power or control circuit
Failing or shorted internal regulator or FET inside the control module
Stuck or welded relay supplying module power
Corroded/damaged connector or wiring harness causing incorrect voltage reading
Charging system over-voltage (faulty alternator/regulator)
Incorrect or incompatible replacement module or aftermarket modification tied into the circuit

Stored B3A28 code and possible related body/module warnings
Active aerodynamic system inoperative or stuck in one position
Instrument cluster message or reduced functionality for aerodynamic features
Intermittent or permanent loss of module communication with BCM/TCM (network symptoms)
Possible battery/charging system warnings if alternator over-voltage present

Retrieve all stored/related codes and freeze-frame data with a scan tool
Visually inspect module B connector, wiring, and harness for damage, corrosion or aftermarket splices
Measure battery resting voltage and charging voltage at battery posts (key off and engine running)
Back-probe module B power pin with key ON and engine OFF/ON to compare with battery voltage
Disconnect the module B main connector and measure voltage at harness power feed to see if high voltage persists
Check relevant fuses and power relays for correct operation and signs of overheating or welding

Battery voltage (nominal, key ON engine OFF): ~12.0–12.8 V
Charging voltage (engine running): typical 13.5–14.8 V — sustained voltage above ~16 V indicates over-voltage fault
Module power feed expected to match battery/ignition supply and not exceed charging voltage by more than a small margin
Control/sense inputs (logic) typically 0–5 V; any substantially higher voltage is abnormal
High-voltage fault threshold: module flags circuit when measured voltage exceeds its designed upper limit (consult OEM spec for exact value; commonly >15–16 V)

Read all DTCs and live data, record freeze-frame values and voltage readings when the code set. Note key-on/key-off/engine-running voltages.
Perform a thorough visual inspection of wiring, connectors, and module B. Look for melted insulation, corrosion, pin damage, or aftermarket taps.
Verify battery condition and charging system: measure battery resting voltage, then charging voltage with engine running; address any alternator/regulator over-voltage first.
With key ON, back-probe the module B power pin and compare directly to battery positive. If harness voltage is higher than battery/charging voltage, suspect an external feed or measurement error upstream.
Disconnect the module B connector and measure the harness power feed: if the harness still shows high voltage, locate short/incorrect feed source (fuse box, relay, aftermarket device). If the harness voltage falls to normal with connector disconnected, suspect internal module fault.
Check fuses/relays supplying module B for proper operation and contact resistance. Replace suspect relays and retest.
Inspect and test ground circuits for low resistance to chassis/negative battery terminal.
If wiring and external supplies check good, consider swapping with a known-good module or replacing module B per manufacturer procedure. Reprogram/initialize if required.
Clear codes and retest to confirm repair. Monitor for recurrence and re-check charging system under load.