What does the B0039 fault code mean?
The B0039 fault code, applicable to all car manufacturers, means “Second Row Right Frontal Stage 1 Deployment Control (Subfault)“.
Background Information: Newer vehicles use multi-stage airbags to regulate the pressure within the airbag. The higher the pressure, the greater the intensity of the airbag deployment. The system automatically determines the airbag deployment intensity based on parameters such as collision intensity, passenger weight, seat belt usage, child seat presence, and distance from the airbag. This design ensures that the airbag deploys at medium intensity in most collisions, reserving maximum intensity for the most severe collisions.
Common Symptoms when B0039 is present:
- The airbag warning light on the dashboard remains illuminated, indicating a fault in the airbag system.
- The driver may experience intermittent airbag system problems during testing, such as occasional warning lights or unresponsive airbags.
- Increased risk of airbag failure during an accident, potentially leading to serious injury.
- Potential problems with the vehicle’s safety system, leading to a lack of confidence in overall vehicle safety.
- Electrical problems within the vehicle, such as flickering lights or dashboard display malfunctions, may also be present.
Most Common Causes of B0039 (in order of frequency):
- Damaged wiring or connectors (60%): Corroded or broken wiring harnesses can lead to poor connections, affecting the airbag system.
- Airbag control module failure (25%): If the control module malfunctions, it may not be able to receive or send the correct airbag deployment signals.
- Airbag sensor failure (10%): The sensor that detects collision force may fail, preventing the airbag from deploying in an accident.
- Improperly installed aftermarket parts (3%): Improper modifications or repairs can interfere with the airbag system.
- Manufacturing defects (2%): In rare cases, defects in airbag system components may cause this code.
B0039 Diagnostic and Repair Procedure:
- Connect a dedicated SRS scan tool (e.g., an airbag scanner with an SRS module). Read the B0039 code and any related codes that may indicate a related circuit fault (such as B0038, B0040).
- Perform a bidirectional test on the second-row right front airbag circuit. The tool should command the module to send a “test pulse” and verify the voltage at the airbag connector (typically 12 V ± 0.5 V).
- Check the wiring and connectors for wear, corrosion, or broken pins. Use a multimeter to check the continuity from the SRS control unit to the airbag connector; the resistance should be less than 5 Ω.
- Verify the power supply by measuring the voltage at the module power pins (with the ignition switch on). A voltage below 11.5 volts indicates a power supply problem that must be resolved before further testing.
- Verify the module software version against the manufacturer’s latest version. If the version is outdated or the flash process was interrupted, reprogram the module using OEM-approved calibration files.
- Perform the “clear codes and retest” procedure after repairs. If the B0039 code returns after a complete drive cycle, the fault is most likely in the module itself.
- Repair vs. Replacement – Minor wiring repairs and successful reprogramming can restore functionality if the internal circuitry of the module is intact. However, when continuity tests reveal intermittent resistance, voltage drops, or the module fails bidirectional testing after reprogramming, replacement is the safer option.
B0039 Code Frequently Asked Questions
What does the B0039 code mean for my car?
The B0039 code indicates a malfunction in the driver’s side airbag deployment control circuit. This issue could prevent the airbag from deploying in an accident, increasing the risk of injury. It is crucial to address this problem to ensure the airbag system functions correctly in the event of a collision.
How much does it cost to repair the most common causes of B0039?
Common causes of B0039 include damaged wiring (60%), airbag control module failure (25%), and airbag sensor failure (10%). Repair costs can vary; for example, wiring repairs might cost between $100 and $300, while replacing the airbag control module could cost between $400 and $600.
Can I drive with a B0039 code, or should I stop immediately?
Driving with an active B0039 code is not safe, as it indicates a problem with the airbag system that could prevent the airbag from deploying in an accident. It is recommended to have the problem diagnosed and repaired before driving.
How do I diagnose B0039 myself with an OBD2 scanner?
To diagnose B0039 with an OBD2 scanner, connect the app to your vehicle’s OBD2 port. Retrieve the trouble code and review the freeze frame data for context. Follow diagnostic procedures to inspect the wiring, connectors, and components related to the airbag system.
Which vehicles are most commonly affected by B0039?
Common vehicles with the B0039 code include 2013-2017 Ford F-150s. If you own a similar model, be aware of any recalls or technical service bulletins related to the airbag system.
How can I prevent B0039 from happening again?
To prevent B0039 from recurring, regularly inspect the airbag system’s wiring and connectors, avoid modifications that could interfere with the airbag system, and ensure all repairs are performed by qualified technicians.
Drivers who see the airbag warning light illuminate after recent maintenance, a minor collision, or even without any apparent event should treat the B0039 code as a safety priority. The warning light may flash briefly before remaining steady, and in severe cases, the airbag may fail to deploy if there is a frontal impact on the passenger side second row right side. Since the airbag system is a passive safety device, it should be addressed immediately.