Airbag warning light on? Causes, MOT rules and what to do in the UK
Direct answer: The airbag / SRS lamp means the Supplementary Restraint System has logged a fault — from a loose seat plug to crash data in the ECU. It is not normal if it stays on after the ignition self-test. In the UK, an SRS malfunction indicator showing a system malfunction is a Major MOT defect. Scan the airbag module, repair the real cause, then clear codes. Do not wipe the lamp the night before the test and hope.
Key takeaways
- Brief lamp at ignition on is normal. Lamp that stays on, comes on while driving, or returns after a clear is a fault.
- MOT fail = SRS malfunction lamp. Passenger bag “off” switch lamp is a different rule.
- Not every SRS lamp means the ECU needs a crash-data reset — especially if the car has never been in a smash.
- A cheap engine OBD reader is the wrong tool.
- Drive it if you must, but do not assume the bags will fire next time.
This is the MOT and general-causes page. Bags already replaced and the lamp still on: diagnosis after airbag replacement. Reset versus a new module: repair vs replacement.
What the airbag warning light means
Dash wording varies: airbag icon, SRS, a seated figure, “Airbag Fault”, “Restraint System Fault”. At key-on the lamp should light for a self-test, then go out. If it stays, flashes, or returns after someone “cleared it”, the control unit has a stored or live fault.
SRS is the Supplementary Restraint System: bags, pretensioners, crash sensors, occupancy, clock spring, looms, and the airbag ECU. One open circuit in that network is enough to keep the lamp on.
Is an airbag light an MOT failure in the UK?
Yes — if it is a malfunction lamp. The MOT inspection manual for cars and passenger vehicles classifies an SRS malfunction indicator that indicates a system malfunction as a Major defect. The vehicle will not pass with that present.
The tester is looking at what the lamp is telling you, not whether you dislike orange icons:
| What you see | Typical MOT view |
|---|---|
| SRS / airbag malfunction lamp on (system fault) | Major defect — fail |
| Passenger airbag deliberately switched off (status lamp only) | Not treated as an SRS system defect by itself |
| Lamp comes on at ignition then goes out | Normal self-test |
Common causes — including when there was no accident
| Cause | When it shows up | First move |
|---|---|---|
| Crash data in the SRS ECU | After a collision, even once bags are fitted | Scan; if that is all that remains, original ECU reset |
| Fired pretensioner or open bag circuit | After a smash, or a botched repair | Fix the pyrotechnic / circuit — do not reset first |
| Connector under the seat | After the seat was slid, valeted, or a child seat fitted | Inspect yellow SRS plugs and occupancy wiring |
| Occupancy / passenger mat | Passenger bag codes, no crash history | Diagnose the seat; some cars need calibration |
| Clock spring | Driver bag / horn / buttons after steering work | Inspect the column cassette |
| Impact sensor or loom | After bumper, sill or water damage | Test sensor and wiring, not “sensor = new sensor” |
| Low battery / jump start | Lamp after a flat battery | Scan anyway — voltage codes exist, guessing is not a fix |
| ECU internal fault | No comms, water, impact on the module | Repair or replace — not a crash-data-only job |
| Unknown history on a used car | Bought with the lamp on, or it appears after a week | Full SRS scan; assume nothing about previous repairs |
Can you drive with the airbag light on?
The engine will usually still run. That is not the same as the car being safe. While the SRS is in fault, you should not assume bags or pretensioners will operate in another impact. Get it scanned. If an MOT is due, get it repaired first — a Major defect is a fail, not a warning advisory.
How you fix an airbag warning light
There is no universal “reset the light” trick. Sequence:
- Read SRS codes with a tool that talks to the airbag ECU. Record them before anyone clears them.
- Investigate that circuit — bag, belt, sensor, plug, clock spring, occupancy, or the module itself. The code names a circuit, not always a dead part.
- Repair the hardware. Pyrotechnics and SRS looms are safety-critical.
- Crash data only if that is what is left after an accident repair. Compatible original modules can be posted to East Grinstead for bench reset and tracked UK return.
- Refit, rescan. If the lamp returns on the same cycle, the fault is still live.
Bags already in and lamp still on — use the step-by-step diagnosis article, not a second copy of this page.
If the scan shows crash data on a serviceable original ECU, send the part number (photo of the label), registration and codes. Quotation by email or text.
Get a quotationOBD2, battery disconnect, DIY clears
A supermarket OBD dongle is for engines. Crash data often cannot be erased from the socket even with a dealer-level tool. Disconnecting the battery does not wipe the ECU and does not repair a fired pretensioner. If the lamp comes back after a clear, stop clearing it.
Never assume every SRS lamp needs a module reset. No accident history usually means wiring, occupancy, clock spring or voltage — scan first.
If the remaining job is the original ECU
Reset My Airbag serves private owners, garages, bodyshops and accident repair centres across the UK from East Grinstead, West Sussex. Send make, model, year, ECU label photo, accident/deployment notes and SRS codes. Many units turn around same day or 24–48 hours, 24-month warranty on the reset or repair. After refit, scan the whole system before MOT or handover.
Frequently asked questions
Will an airbag warning light fail an MOT?
Yes, if it is an SRS malfunction lamp indicating a system fault — Major defect. A passenger-bag-off status lamp is treated differently.
Why has my airbag light suddenly come on?
SRS logged a fault. Everyday causes: seat connectors, occupancy mat, clock spring, low voltage. After a crash: crash data or fired hardware. Scan the airbag ECU.
How do I get the airbag light to turn off?
Diagnose, repair, then clear. If crash data remains in a compatible original module, that is a specialist reset — not a code wipe.
Can a low battery cause the airbag light?
It can store voltage-related codes. Still scan. Do not replace the battery and assume the SRS is healthy.
Is it safe to ignore it?
No. You cannot assume the restraint system will work. It will also fail MOT if it is a malfunction lamp.
Can an airbag module be reset after an accident?
Many original ECUs can, if they are compatible and the rest of the system is already repaired. See repair vs replacement for reset / repair / new box.
SRS components are pyrotechnic and safety-critical. Clearing a lamp is not a repair. Work on the system only if you are competent.