B3A51
Low Severity (Level 2)Active Aerodynamic Feature C Position Sensor 2 Circuit Low Voltage
B3A51 usually means active Aerodynamic Feature C Position Sensor 2 Circuit Low Voltage.
Can you still drive with B3A51?
⚠️Short-distance driving is usually OK, but have this diagnosed within a week to prevent further damage.
Typical repair cost: $50 – $600
Severity Level 2 — Low
This code indicates a minor issue that is unlikely to cause immediate driveability problems. You can typically continue driving but should have the vehicle inspected at your earliest convenience.
Common Symptoms
- Body accessories reading zero or abnormally low
- The body accessory system is not operating as designed
- Warning light or malfunction indicator related to the body accessory system is illuminated
- Diagnostic trouble code (DTC) stored in module memory
Possible Causes
- Failed body control module or accessory module — internal resistance has increased, outputting a signal lower than specification
- Damaged wiring or corroded connector in the body accessory system circuit introducing high resistance
- Short to ground in the body accessory system signal wire — wire chafed through, signal voltage pulled low
- Loose or oxidized ground connection for the body control module or accessory module — clean the ground and retest before replacing parts
- Low system voltage (weak battery or failing alternator) causing sensor reference voltage to sag
Common Fixes
- Scan vehicle with a professional-grade OBD2 scanner to read all stored codes and freeze frame data — note the conditions when the code set ($42-103 at shop, free at auto parts store for basic scan)
- Visually inspect the body accessory system wiring harness and connectors — look for chafed wires, melted insulation, green corrosion, loose pins, or rodent damage (often free to check yourself, $100 diagnostic fee at shop)
- Test body control module or accessory module with a multimeter at the connector — compare readings to factory service manual specs. If out of spec, replace body control module or accessory module ($50-600)
- Check the reference voltage supply to body control module or accessory module — should be steady 5V (or 12V) — if low, trace back to PCM/BCM voltage regulator ($156-404 if module repair needed)
- Perform a voltage drop test on the ground side of the body accessory system circuit — more than 0.1V drop means a bad ground that must be cleaned/repaired ($91-189 at shop)
Estimated Repair Cost
These are estimated costs based on generic repair data. Actual costs may vary depending on your vehicle, location, and labor rates.
Frequently Asked Questions
What does B3A51 mean?
B3A51 stands for "Active Aerodynamic Feature C Position Sensor 2 Circuit Low Voltage". B3A51 usually means active Aerodynamic Feature C Position Sensor 2 Circuit Low Voltage.
Can you drive with B3A51?
Short-distance driving is usually OK, but have this diagnosed within a week to prevent further damage.
How much does it cost to fix B3A51?
Repair costs for B3A51 typically range from $50 to $600, depending on your vehicle make, model, and local labor rates. Common fixes include: Scan vehicle with a professional-grade OBD2 scanner to read all stored codes and freeze frame data — note the conditions when the code set ($42-103 at shop, free at auto parts store for basic scan); Visually inspect the body accessory system wiring harness and connectors — look for chafed wires, melted insulation, green corrosion, loose pins, or rodent damage (often free to check yourself, $100 diagnostic fee at shop); Test body control module or accessory module with a multimeter at the connector — compare readings to factory service manual specs. If out of spec, replace body control module or accessory module ($50-600).
Will B3A51 clear itself?
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