Why is my airbag light still on after replacing the airbags?
Direct answer: New bags do not reset the Supplementary Restraint System. The SRS ECU often still holds crash data, or something else that fired or broke is still in circuit — pretensioners, impact sensors, clock spring, occupancy mat, a wrong-part bag, or a connector knocked off during the strip. Scan the airbag module with a proper SRS tool before you send the ECU. If the only remaining story is crash data on a serviceable original module, that is a specialist bench reset, not a dealer box.
Key takeaways
- Fitting airbags is one job. Signing the SRS off is another.
- A basic OBD engine reader will not tell you why the lamp is on.
- Record codes first. Clearing them is not a diagnosis.
- Do not post the ECU while pretensioners or sensors are still faulty — the lamp will come back.
- An SRS malfunction lamp is a Major MOT defect in the UK.
This page is for the car that already has new bags in and the lamp still lit. If you are choosing reset versus a new ECU, use airbag ECU repair vs replacement. MOT lamp categories in more depth: airbag warning light, causes and MOT rules.
What happens when airbags deploy
In milliseconds the SRS can fire driver, passenger, side, curtain or knee bags and the seat-belt pretensioners. The airbag control module (SRS ECU) logs that event as crash or deployment data. Swapping the visible bags does not wipe that memory. It also does not fix a pretensioner that fired and was left in the car.
Why the lamp is still on — cause versus next step
| Likely cause | Typical clue | Do this |
|---|---|---|
| Crash data still in the original ECU | Bags and belts already correct; codes mention crash / deployment / stored event | Photograph the ECU label, send the original module for bench reset if compatible |
| Pretensioner still fired or open circuit | Belt locked, burnt connector, B-pillar or buckle codes | Repair or replace the pretensioner. Do not reset the ECU first |
| Impact / satellite sensor | Front, side or satellite sensor codes; crush in bumper or sill | Test the sensor and loom. A code is not a parts list |
| Wiring or connector | Intermittent lamp after interior strip; codes change when a seat is moved | Check under seats, dash, yellow SRS plugs, clock-spring connector |
| Wrong or incompatible bag | Lamp appeared the moment the new bag was plugged in | Match part number, year and trim — similar plastic is not the same bag |
| Clock spring | Driver bag / horn / steering-angle codes after airbag or column work | Inspect the clock spring; do not keep clearing the code |
| Occupancy / seat mat / seat position | Passenger bag codes with no dash-bag work | Diagnose the seat circuit. Recalibration may be required on some cars |
| ECU internal fault (not just crash data) | No communication, internal failure, water or impact on the module | That is repair or replace — see the repair vs replacement guide |
| Used or new ECU fitted without coding | Lamp after a breaker or dealer module swap | Coding/VIN match, or put the original back and reset that instead |
How to find out why it is still on
- Scan the SRS, not the engine. Use a tool that opens the airbag control unit. Write the codes down before anyone presses clear.
- List what actually fired. Driver, passenger, curtains, pretensioners, sensors already replaced — so you are not guessing.
- Diagnose each live code. The component named in the text is a starting point, not an order form. Check the loom.
- Decide if crash data is all that is left. If hardware is correct and the module still reports a stored crash event, the original ECU can often be reset on the bench in East Grinstead and posted back UK-wide.
- Repair the rest, then rescan. If you clear codes and the lamp returns in the same ignition cycle, the fault is still live.
Send registration, ECU part number (photo of the label), which bags fired, and the SRS codes via the quotation page.
Get a quotationOBD2 scanners, disconnecting the battery, second-hand modules
Can I clear it with a cheap OBD2 reader?
Usually no. Those tools read the engine. SRS needs an airbag-capable interface. Even then, crash data is often locked in the ECU and will not wipe from the OBD socket.
Will disconnecting the battery reset the light?
No. The crash record lives in the module. Battery disconnect does not repair pyrotechnics or sensors.
Can I use a second-hand airbag module?
High risk: donor crash lock, wrong hardware index, VIN coding. Keeping and resetting the original unit is usually cleaner — full comparison on repair vs replacement.
Is an airbag light an MOT failure?
Yes, if the SRS malfunction indicator shows a system malfunction — that is a Major defect in the MOT inspection manual for cars and passenger vehicles. A lamp that only shows the passenger airbag has been switched off on purpose is treated differently. Do not present the car until the system is actually repaired.
What to send us if the remaining job is the ECU
Reset My Airbag works with private owners, garages, bodyshops and accident repair centres across the UK. Modules come into East Grinstead, West Sussex, and go back tracked.
- Make, model, year and registration
- Photo of the SRS ECU part-number label
- Which airbags and pretensioners deployed
- The SRS fault codes from a proper scan
Typical turnaround on many units is same day or 24–48 hours once the module is here, with a 24-month warranty on the reset or repair. After refit, scan the whole SRS again before you sign the job off.
Frequently asked questions
Why is my airbag light still on after replacing the airbags?
Because the SRS is more than the bags. Crash data, pretensioners, sensors, clock spring, occupancy and wiring all set the same lamp. Scan first.
Does the airbag module need resetting after the bags deploy?
Often, if the original ECU stored crash data and the rest of the system is already repaired. Not every remaining lamp is crash data.
Can I reset the airbag light with a diagnostic scanner?
Ordinary codes, after a real repair, yes with the right tool. Crash data in the ECU usually needs a specialist bench reset.
Why does the light come back after I clear it?
The fault is still active. Stop clearing and diagnose the live code.
Do seat belt pretensioners need replacing after an accident?
If they fired or test faulty, they need professional repair or replacement. Leaving them and resetting the ECU will not pass the system.
Will my car pass an MOT with the airbag light on?
Not if the SRS lamp indicates a system malfunction — Major defect. Get it diagnosed properly.
Airbags and pretensioners are pyrotechnic, safety-critical parts. The car is not roadworthy because someone cleared a code. Work on the system only if you are competent to do so.