OBD-II trouble code
B0020: Left Side Airbag Deployment Control (Subfault)
The airbag/SRS control module detected an electrical fault in the left-side airbag deployment loop. Side-impact protection on that side may not deploy as designed, so this needs prompt professional attention.
Quick facts
- System
- Body
- Category
- Airbag / SRS Restraints
- Severity
- High severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $100 – $900
- DIY difficulty
- Shop recommended
What does B0020 mean?
B0020 is a body (B) code stored by the airbag control module. Its SAE-generic definition is 'Left Side Airbag Deployment Control,' referring to the firing loop that deploys the left-side (driver-side) side-impact airbag — the thorax or seat-mounted side bag that protects an occupant in a side collision. The module monitors this deployment loop continuously and stores B0020 when its electrical condition is wrong. As with all B-codes, the exact application varies by manufacturer; some GM tables list B0020 as a passenger instrument-panel deployment loop, so confirm the definition against your make's service data.
The module sets the code when the deployment loop's resistance moves outside the narrow range these pyrotechnic circuits demand — an open circuit, a short to power or ground, or resistance too high or too low. Manufacturers add a symptom byte (for example open circuit, short-to-ground, or resistance out of range) that identifies the exact fault, so read the full code including its suffix. Because side airbags are frequently mounted in the seat, their firing loop passes through connectors under the seat that can back out, corrode, or be disturbed during seat removal or upholstery work.
This is a supplemental restraint fault, not a driveability fault: the vehicle drives normally, but the left-side airbag may not deploy as intended in a crash, and airbag circuits carry a small risk of unintended deployment when mishandled. SRS diagnosis and repair should be performed by a qualified technician who can safely disable the system, and the fault should not be left unrepaired.
Common causes
- Corroded, backed-out, or loose connector under the seat or at the side airbag
- Damaged wiring in the side-airbag firing loop (flex fatigue at the seat harness is common)
- Failed side-airbag inflator (squib)
- Seat removal, upholstery, or occupant-sensor work that disturbed the loop or connector
- Fault in the SRS connector or its shorting clip at the airbag
- Faulty airbag/SRS control module
Symptoms
- Airbag / SRS warning light on
- Stored B0020 fault (often with a symptom byte) in the restraints module
- No effect on engine or driving performance
- Fault may appear or clear as the seat is moved if a connector is intermittent
Diagnostic steps
- 1.Use a scan tool that can access the airbag/SRS module and record B0020 with its full symptom byte and any companion codes.
- 2.Confirm the exact loop location for the specific make and model, since B0020 maps to different airbags across manufacturers.
- 3.With the system safely disabled per service procedure, inspect the connector under the affected seat and the side-airbag connector for corrosion, backed-out terminals, or damage.
- 4.Gently flex the seat harness while monitoring, since side-airbag loops are prone to intermittent connections where the harness bends.
- 5.Measure the deployment-loop resistance against specification to separate a wiring/connector fault from a failed inflator.
- 6.If the seat, airbag, or module was recently serviced, verify the correct part and proper connection.
- 7.Repair the wiring/connector fault or replace the indicated component, then clear codes and confirm the SRS light stays off.
Repair cost
$100 – $900
Reseating or repairing a corroded under-seat connector can be inexpensive, while a failed side-airbag inflator or control module is far costlier. SRS diagnostic time typically runs $100-$200, and a side airbag or SDM/RCM replacement with programming can reach several hundred dollars or more. SRS work should be done by a qualified technician.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with airbag control module (sdm) replacement / reset preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
Leave this one to a qualified shop. It typically involves emissions-critical components, refrigerant handling, or other work that requires manufacturer-grade tooling, training, or certification. DIY attempts often produce a more expensive problem than the original code.