B0001 to B0100: airbag and restraint system codes explained

B-codes are body codes, and the B00xx range covers the supplemental restraint system: airbags, seat belt pretensioners, occupant sensing, and the module that controls them.

Range	Typically covers
B0001–B0010	Driver airbag deployment loops
B0011–B0020	Passenger airbag loops
B0020 onwards	Side, curtain and knee airbags
B0050 onwards	Seat belt pretensioners and buckle switches
B0080 onwards	Occupant classification and sensing

Exact assignments vary by manufacturer. Read the description your tool provides for your specific vehicle.

Related: airbag light on causes and B1000 body control codes explained.

Generic OBD-II usually cannot read these

Worth knowing before you try.

OBD-II mandates access to emissions-related data. Airbags are a safety system, not an emissions system, so there is no requirement to expose them through the generic interface.

Most vehicles keep restraint codes in a module that needs manufacturer-level access. A generic adapter typically reports “no codes” while the airbag lamp is lit — and that is not a fault in the adapter.

Scan tool limits: what OBD cannot see.

Why the lamp matters more than most

Every other warning lamp tells you something is not working now. This one tells you something may not work during a collision.

A restraint system with a stored fault typically disables the affected device. An airbag that does not deploy, or a pretensioner that does not tighten, changes the outcome of an accident.

This is not a lamp to live with, and in many markets it is an automatic inspection failure.

The common causes, and they are mostly connectors

Seat connectors

The connector under the front seat carries the side airbag, the pretensioner, the occupant sensor and the seat heater. It gets flexed every time the seat is moved.

Sliding the seat fully forward and back repeatedly is one of the most common causes of an airbag lamp, and vacuuming under the seat catches the connector often enough to be worth suspecting.

The clockspring

The driver airbag connects through the coiled ribbon cable in the steering column. Clocksprings wear out with steering rotation.

The tell: horn and steering wheel controls failing at the same time: horn and clockspring faults and U0126 lost communication with steering angle.

Water

Restraint modules are often mounted low, under the centre console or beneath a seat. A leaking heater matrix, a blocked scuttle drain or a failed door seal puts water there.

Damp carpet plus an airbag lamp is one fault: damp carpet and electrical faults and water leak into cabin.

The occupant classification system

Passenger seat sensors decide whether to deploy the passenger airbag and with what force. Their mats and sensors fail, and heavy items left on the seat can confuse them.

Child seats and airbag safety.

Low system voltage

A weak battery produces module faults across the car, including here. Check voltage before diagnosing anything: P0560 to P0563 system voltage.

After a deployment, or a suspected one

This is the used-car angle, and it is serious.

A deployed restraint system requires the airbags, the pretensioners and usually the control module to be replaced. The module records a crash and is generally not resettable — for good reason.

Modules are nonetheless sometimes “reset” or replaced with used units from another vehicle to make the lamp go out on a car being sold.

Checks before buying:

1. Ignition on: the airbag lamp must illuminate, then go out. A lamp that never illuminates has been disabled.
2. Look for mismatched trim, new bolts, or replaced steering wheel and dashboard sections.
3. Have the restraint system scanned with equipment that can read it.
4. Check the vehicle history: vehicle history check before buying and US salvage import OBD diagnostics.

After a minor accident, what to check.

Safety when working on it

Restraint systems contain pyrotechnic devices. Before disconnecting anything:

• Disconnect the battery and wait for the reserve capacitor to discharge — typically several minutes, sometimes longer.
• Never probe the deployment loops with a multimeter. The current can be enough to fire the device.
• Handle removed airbag modules facing away from you.

If that sounds like a reason to leave it to a workshop, it is.

Try it on the free tier of the app — pair an ELM327 adapter for engine and emissions work, and be aware that restraint codes usually need manufacturer-level access. Knowing that boundary before you need it saves confusion at the worst moment.