Poor connection or damaged connector at the left seat, door pillar or side airbag module (corrosion, loose or pushed-back terminals); Damaged wiring in the deployment loop, for example chafed or broken wires in the seat base, door hinge area or pillar; Faulty left side airbag module or squib with incorrect internal resistance; Seat connector unplugged or disturbed after seat removal, trim work or upholstery repair; Damage or water ingress after a previous collision, repair or flood; Faulty restraint control module or an outdated module calibration, where the manufacturer lists it as a known cause for the model.

B0020

Left Side Airbag Deployment Control.

Generic
Body
Generic code
High severity

How this code is built

B: SystemBody
0: Defined bySAE, the same on every car
0: AreaBody area 0
20: FaultThe specific fault in that area

What it means

B0020 is the generic code for a fault in the left side airbag deployment control circuit. The restraint control module (SRS) checks the resistance and voltage of the deployment loop (the squib or igniter, its wiring and connectors) during its self-test. It set the code because the reading was outside the expected range, such as an open circuit, a short to ground, a short to voltage or an incorrect resistance. The exact fault type and which airbag it covers (side, curtain or thorax) depend on the vehicle.

Symptoms

Airbag (SRS) warning light on, or flashing, in the instrument cluster
Left side airbag may be disabled and may not deploy in a crash
Airbag light may come and go, often when a seat is moved or a door is slammed
Seat belt pretensioner or other restraint faults stored alongside the code
Fails an inspection because of the lit SRS warning

Possible causes

Poor connection or damaged connector at the left seat, door pillar or side airbag module (corrosion, loose or pushed-back terminals)likely
Damaged wiring in the deployment loop, for example chafed or broken wires in the seat base, door hinge area or pillarlikely
Faulty left side airbag module or squib with incorrect internal resistancepossible
Seat connector unplugged or disturbed after seat removal, trim work or upholstery repairpossible
Damage or water ingress after a previous collision, repair or floodpossible
Faulty restraint control module or an outdated module calibration, where the manufacturer lists it as a known cause for the modelrare

How to diagnose

Read all stored and pending codes and freeze frame data, and note whether B0020 is current or history and whether other SRS codes are present
Ask about recent work on the car, such as seat removal, trim or upholstery repairs, a collision or water damage
Make sure the battery is disconnected and the manufacturer's waiting time has passed before touching any airbag connector
Visually inspect the left side airbag wiring and connectors, including under the seat, the door pillar and the yellow SRS connectors, for damage, corrosion and seating
Check the connector locks and shorting clips for damage, following the manufacturer's procedure
Use the manufacturer's procedure and live data to look at the loop resistance or status, without probing the airbag directly with a meter
Wiggle-test the harness with live data on the scan tool to find intermittent faults
Check for manufacturer service bulletins or calibration updates for the model and code

How to fix

Repair or replace damaged wiring in the deployment loop using the manufacturer's approved method, not ordinary joins
Clean, re-seat or replace faulty connectors and terminals
Replace the left side airbag module or squib if it is confirmed faulty, following the manufacturer's safety procedure
Refit and secure any disturbed seat or pillar connectors correctly
Replace or recalibrate the restraint control module only if testing confirms it is at fault or an update is specified for a known fault, then clear codes and confirm the SRS light stays off

Can I keep driving?

High severity

The car will usually still drive normally, but the left side airbag may not deploy in a crash, so treat it as a safety fault. Get it inspected and repaired promptly and avoid carrying passengers on that side until it is fixed.

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