B0031 – Left Side Airbag Deployment Loop indicates that the Supplemental Restraint System (SRS) module has detected a fault in the left-side airbag firing circuit. This loop controls the deployment of the driver-side seat-mounted or door-mounted side airbag, which is designed to protect you during side-impact collisions. When the SRS module detects abnormal resistance, opens, or shorts in this loop, the airbag warning light activates and the airbag may be disabled. This guide explains the meaning of B0031, along with symptoms, causes, diagnostic steps, and effective repairs.
What Does B0031 Mean?
B0031 is a body-system OBD-II code that appears when the SRS module detects an electrical fault in the left-side (driver-side) airbag deployment circuit. This includes the wiring, connectors, pretensioner pathways (in some designs), and the inflator igniter responsible for firing the side airbag during a crash.
If the circuit is open, shorted, contaminated, or outside the specified resistance range, the SRS module disables the airbag for safety. Because side airbags deploy extremely quickly during collisions, the system must ensure perfect circuit integrity at all times.
Quick Reference
- OBD-II Family: B-Code (Body)
- Scope: Generic
- System: SRS – Left Side Airbag
- Difficulty Level: Moderate–Advanced
- Estimated Repair Cost: €90–€650+
- Last Updated: 27 November 2025
Real-World Example / Field Notes
A crossover arrived with the airbag light illuminated after a recent interior-detailing service. The technician found that the left seat connector had been partially unplugged during vacuuming. Securing the connector, cleaning the terminals, and clearing the fault restored full SRS function.
In another case, a sedan triggered B0031 intermittently. Resistance measurements revealed a broken wire inside the seat harness caused by frequent seat-height adjustments. Repairing the wiring and routing it correctly permanently resolved the fault.
Symptoms of B0031 – Left Side Airbag Deployment Loop
- Airbag warning light: Illuminated on the dashboard.
- Left side airbag disabled: Will not deploy in a side impact.
- Intermittent SRS alerts: Especially when adjusting the seat or hitting bumps.
- Seat wiring disturbances: Issues after seat repairs or cleaning.
- Possible additional SRS codes: Depending on wiring or module issues.
Common Causes of B0031
Most Common Causes
- Loose or partially disconnected seat-airbag connector
- Damaged seat wiring harness from seat movement
- Left side airbag module (igniter) failure
- Corrosion in seat-mounted SRS connectors
- Open circuit caused by broken wires inside seat cushion
Less Common Causes
- SRS control module internal fault
- Water intrusion under the carpet or seat
- Improper installation after upholstery or seat repairs
- Blown seat airbag from previous collision not replaced correctly
- Low system voltage affecting SRS self-tests
Diagnosis: Step-by-Step Guide
Side-airbag circuits must be diagnosed carefully due to the risk of accidental deployment. Always follow SRS-safe procedures.
Tools You’ll Need
SRS-capable scan tool, multimeter with airbag-safe adapters, wiring diagrams, trim tools, torx bits, and insulated gloves.
- Disable the SRS system: Disconnect the battery and wait the manufacturer’s specified time.
- Scan all SRS codes: Confirm B0031 and check for other related airbag or seat faults.
- Inspect left-seat connectors: Ensure the yellow connector is fully locked and clean.
- Check wiring under the seat: Look for pinched, stretched, or frayed wires.
- Measure loop resistance: Only with airbag-approved testing tools.
- Move seat during tests: Identify intermittent opens caused by harness flexing.
- Inspect left-side airbag module: Check for damage or signs of previous deployment.
- Verify SRS module grounds and voltage: Poor grounding can cause false-loop readings.
- Check for water damage: Moisture under the seat can corrode circuits.
- Repair or replace components as required: Then clear the fault and retest.
Pro Tip: If B0031 appears only when the seat is moved forward/backward, the wiring harness is almost certainly strained or internally broken.
Possible Fixes & Repair Costs
- Reconnect/clean SRS connectors: €20–€80
- Repair damaged seat wiring: €40–€150
- Replace left side airbag module: €200–€450+
- Replace seat harness: €120–€300+
- Replace SRS control module: €180–€350+
Can I Still Drive With B0031?
Yes, the vehicle can move, but it is not fully safe. The left side airbag will not deploy during a side impact, which significantly increases injury risk. Some vehicles may also disable the opposite side airbag or seatbelt pretensioner as a precaution. Immediate repair is strongly recommended.
Related Codes
- B0019 – Occupant Restraint Airbag Circuit Fault
- B0018 – Body Circuit Fault — Restraint Sensor Signal
- B0017 – Body Circuit Signal Integrity Fault
- B0016 – Occupant Sensing Circuit Fault (SRS)
- B0014 – Occupant Restraint Circuit Fault
- B0011 – Occupant Restraint Circuit Fault
- B0009 – Restraint System Circuit Fault
- B0008 – Supplemental Restraint System Circuit High
- B0007 – Supplemental Restraint System Circuit Fault
- B0006 – Restraint Deployment Commanded Too Long
Key Takeaways
- B0031 indicates an electrical fault in the left side airbag deployment loop.
- Seat connectors and wiring damage are the most common causes.
- The left side airbag is disabled until repairs are completed.
- Proper SRS-safe testing is essential for accurate diagnosis.
FAQ
Does B0031 disable the left side airbag?
Yes. The SRS module disables the airbag to prevent unsafe deployment.
Is this code dangerous?
Yes. Side airbags play a critical role in preventing injuries during side-impact collisions.
Can moving the seat trigger B0031?
Absolutely. Seat movement commonly stresses the wiring harness and connector.
Is the airbag module usually the problem?
No, wiring or connectors fail far more often than the airbag module itself.
Can water under the seat cause this fault?
Yes. Moisture leads to corrosion and resistance changes in SRS circuits.