Will my car fail its MOT with the airbag light on?

Yes. An airbag warning lamp indicating a malfunction is a major defect, with 84,147 recorded failures in the DVSA data behind this site. The tester switches on the ignition, watches the lamp illuminate as a bulb check and confirms it goes out. A lamp that stays on is a failure. So is one that never comes on at all, because that suggests the bulb has been removed or the warning disabled, and testers are specifically alert to it.

Why is my horn not working with an airbag light on?

Because they share a part. The clock spring is a coiled flat ribbon cable behind the steering wheel that keeps the wheel's electrical circuits connected however far you turn it. It carries the airbag firing circuit, the horn and the steering wheel buttons together. As it ages the ribbon cracks, and a dead horn alongside an illuminated airbag lamp is close to a signature for a failed clock spring. It is a well-defined repair and the part is not among the dear ones.

Is it safe to drive with the airbag light on?

The car itself is unaffected — it drives, brakes and steers exactly as before, and there is no risk of the airbag going off by itself. The risk is the other way round. With the lamp on the system has taken itself out of service, so in a collision the airbags may not deploy at all, and on most cars a fault in one circuit disables the whole system including the passenger and side airbags. You would be driving a car whose restraint system is switched off, which is why this warrants a prompt repair even though nothing feels wrong.

Can I test an airbag circuit with a multimeter?

No, and this is one of the few places where getting it wrong causes injury rather than expense. An airbag is fired by an igniter with a resistance of a couple of ohms, and the test current from an ordinary multimeter can be enough to set it off. An airbag deploying at close range while you are holding it will cause serious injury. Reading the fault codes with a scan tool is completely safe and tells you what you need. Leave resistance testing of deployment loops to people with the right equipment and procedures.

Body code · standard

B0001Driver's airbag circuit fault

Standard definition: Driver Frontal Stage 1 Deployment Control

Last updated 27 July 2026

Quick answer

The airbag control unit cannot verify the driver's airbag deployment circuit. The airbag lamp will be on and, while it is, the system may not fire in a crash — and on most cars it disables the other airbags too.

How the car works this out

Each airbag is fired by an igniter, called a squib, which is a very low resistance element of a couple of ohms. The airbag control unit passes a tiny, harmless current through every deployment circuit continuously and measures the resistance. It knows what a healthy loop looks like and can tell an open circuit, a short to earth, a short to power and a resistance that has drifted out of range. B0001 is that measurement failing on the driver's frontal airbag, stage one. The unit responds by lighting the lamp and, on most cars, disabling the entire restraint system rather than risking a partial or incorrect deployment.

What you might notice

Airbag or SRS warning lamp on and staying on
Horn not working, or steering wheel controls behaving oddly
Cruise control buttons on the wheel unresponsive
Sometimes the stability control lamp too, where the steering angle sensor shares the same assembly
No symptom at all beyond the lamp, which is the usual case

What causes it

Most likely first. A code names the check that failed, not the part that failed it, so more than one of these can produce the same number.

1A worn clock spring, the coiled ribbon connector behind the steering wheel that keeps the wheel's circuits connected as it turnsCommon
How to check: Check whether the horn and the steering wheel buttons still work. The clock spring carries those circuits too, so a dead horn alongside an airbag lamp points at it strongly.
2The yellow airbag connector under the steering wheel not fully latched, often after wheel, column or airbag workCommon
3A failed airbag module, or an aftermarket or secondhand airbag with a different resistancePossible
4An aftermarket steering wheel or boss kit that does not correctly connect the airbag circuitPossible
5A fault within the airbag control unit, common on cars that have been in a previous accidentPossible
How to check: Ask whether the car has a crash record stored. A control unit that has recorded a deployment usually has to be replaced or professionally reset, and it will not clear otherwise.
6Corroded wiring or a damaged loom under the columnLess common

What to do about it

1Do not probe an airbag circuit with a multimeter. Passing a test current through a squib can fire it, and an airbag deploying into your hands at a workbench causes serious injuries. Reading the codes with a scan tool is safe; measuring resistance across a deployment loop is not.
2Get it read properly. The airbag system reports which circuit it is unhappy about, and that narrows the job enormously.
3Check whether the horn and steering wheel controls still work. If they do not, the clock spring is very likely the cause and that is a known, well-defined repair.
4Have the battery disconnected and left for the manufacturer's stated waiting period before any work near an airbag, so the system's reserve power supply discharges.
5Ask about the car's history if the fault will not clear. A control unit that has recorded a previous deployment holds a crash record and will keep the lamp on until it is replaced or properly reset.

Can you keep driving?

Briefly, gently

The car drives, steers and stops normally, so nothing about the journey itself changes. What has changed is what happens if you have an accident: with the lamp on, the system has taken itself out of service and the airbags may not deploy. On most cars that means all of them, not just the one with the fault. That is a risk you carry every mile until it is fixed, and it is the reason to treat this as urgent despite there being nothing to feel.

Will it fail an MOT?

An airbag warning lamp indicating a malfunction is a major defect, recorded 84,147 times in the DVSA data behind this site. The tester checks the lamp comes on with the ignition and then goes out, so a lamp that stays on fails and, importantly, so does one that never illuminates at all — a missing bulb is treated as a malfunction rather than as a clean bill of health. There is a separate defect for an airbag that is obviously missing or has clearly deployed and not been replaced, which is worth knowing if you are buying a car with a suspiciously blank steering wheel centre.

The light this turns on

Airbag warning lightThe supplementary restraint system has found a fault and has almost certainly disabled itself. The car drives exactly as normal, which is what makes this lamp so easy to ignore — but you should assume the airbags and seat belt pretensioners will not fire in a crash while it is lit.

Common questions

Will my car fail its MOT with the airbag light on?: Yes. An airbag warning lamp indicating a malfunction is a major defect, with 84,147 recorded failures in the DVSA data behind this site. The tester switches on the ignition, watches the lamp illuminate as a bulb check and confirms it goes out. A lamp that stays on is a failure. So is one that never comes on at all, because that suggests the bulb has been removed or the warning disabled, and testers are specifically alert to it.
Why is my horn not working with an airbag light on?: Because they share a part. The clock spring is a coiled flat ribbon cable behind the steering wheel that keeps the wheel's electrical circuits connected however far you turn it. It carries the airbag firing circuit, the horn and the steering wheel buttons together. As it ages the ribbon cracks, and a dead horn alongside an illuminated airbag lamp is close to a signature for a failed clock spring. It is a well-defined repair and the part is not among the dear ones.
Is it safe to drive with the airbag light on?: The car itself is unaffected — it drives, brakes and steers exactly as before, and there is no risk of the airbag going off by itself. The risk is the other way round. With the lamp on the system has taken itself out of service, so in a collision the airbags may not deploy at all, and on most cars a fault in one circuit disables the whole system including the passenger and side airbags. You would be driving a car whose restraint system is switched off, which is why this warrants a prompt repair even though nothing feels wrong.
Can I test an airbag circuit with a multimeter?: No, and this is one of the few places where getting it wrong causes injury rather than expense. An airbag is fired by an igniter with a resistance of a couple of ohms, and the test current from an ordinary multimeter can be enough to set it off. An airbag deploying at close range while you are holding it will cause serious injury. Reading the fault codes with a scan tool is completely safe and tells you what you need. Leave resistance testing of deployment loops to people with the right equipment and procedures.

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