SRS Light!

We went for a drive Sat evening just adding for miles. 

Rear suspension bottomed 3 times over different canyons that remained invisible on what Bucks council consider a road surface. 
Almighty crash that sounded like the rear had parted company.  After the second the SRS light was on
Bu**er!   Light glowed merrily all the way home. 
Turned off then on again and it vanished.  So not a loose connection.
Is it possible that the impact is such that the ECU thing we may have had an accident?  But, fortunately, Not enough to fire the bag?
One of the bangs was half way up Kop Hill which hosts an annual hill climb.  That would be fun on an old vintage bike!

https://kophillclimb.org.uk/

 

If light vanished after restart then SRS ECU did not record impact. If SRS ECU fired any of airbags or pretensioners it would be written within SRS ECU and light would stay on to remeber to replace ECU as well.
To me this looks like connection that was dislogged but after restart returned to proper connection (in other words connection was slowly moving to connected state after the Bang).

I also think it was the connection under the seat that got a clout from a seat rail or similar.
Easy enough to give them.a nudge together.

Roverlike - what other connections are you aware of please? 

Brian -  That's my guess as well.  I had to take the seats out to fit the green seatbelts.  That was a strange connector so I'll give it a prod.   I'm always very wary about faffing with the air bag.       



 

Pretensioners connectors, rotary coupler 2 connectors, connector of the SRS ECU itself. 

However underseat connector is the main suspect since when you hit the hole on the pathway connector under seat will suffer. Since they are delicate might loose proper connection and then regain it again.

If the underwear sensor (or whatever it is that triggers the air bag) is so sensitive it begs the question “ How do you disable it and forget it?”. Whilst that might not be an ideal thought or course of action to adopt it is one that in practice might become necessary based on road condition.

I can’t have that interrupting a “touring holiday” just because of road conditions. It’s not acceptable. The car must go i.e. run even if the air bag has fired. We must be able to override that in any ECU.
So how is it done either before or after triggering the SRS ?
A replacement ECU is not something to be undertaken in “the middle of nowhere” on a dark wet night.

Delbourt wrote:

If the underwear sensor (or whatever it is that triggers the air bag) is so sensitive it begs the question “ How do you disable it and forget it?”. Whilst that might not be an ideal thought or course of action to adopt it is one that in practice might become necessary based on road condition.

I can’t have that interrupting a “touring holiday” just because of road conditions. It’s not acceptable. The car must go i.e. run even if the air bag has fired. We must be able to override that in any ECU.
So how is it done either before or after triggering the SRS ?
A replacement ECU is not something to be undertaken in “the middle of nowhere” on a dark wet night.

I do not understand your question in relation to what I wrote if this was question for me? If it was for me, then I think that you did not catch what I said in my answer.

As others have mentioned, the most likely culprit is one of the under seat connectors.

If the airbag ECU looses connection to any of the airbags or pretentioners, even for a fraction of a second, it will turn on the warning light, and the light will remain on for the rest of the journey (even if the issue has long since resolved itself).

Once the car is turned off, and started up again, if all the connections are okay at that point the light will remain off.

Given it was an explainable a one off, I probably would even spend time investigating further, but you could disconnect the battery, wait 15 minutes, disconnect both seatbelt pretentioners, check the contacts for any signs of corrosion, perhaps given them both a quick spray with some contact cleaner, then reconnect.

The crash sensor which is responsible for firing the airbag/s and seatbelt pretensioners in the event of a collision is regarded as generally reliable on our cars. Ive never read of one misbehaving or its connector shorting out and thus firing the SRS system whilst merrily driving along.

The connections to the seatbelt pretensioners can fail sometimes when the seat is moved or the car is driven over bumps but thats neither here nor there. It cant set anything off except the SRS light which only comes on to warn the driver that one of the devices is offline. It certainly isnt a warning that the airbags are about to deploy. Fix the fault and the light goes out everytime.

Roverlike in an earlier post you wrote the following 
“If light vanished after restart then SRS ECU did not record impact. If SRS ECU fired any of airbags or pretensioners it would be written within SRS ECU and light would stay on to remeber to replace ECU as well.”

From that I understood that a spurious fault with one of the sensors such as pre-tensioner or the under seat coupling could initiate a SRS situation where the air bag was “fired”. 
I also then thought that you were saying that if an SRS fault was initiated or that the air bag had fired that the fault could not be cleared from the ECU and/or the ECU might prohibit the car from being driven and that is something that would not be acceptable.
Either there must be a means to override that or a means to easily re set it. 
A serious crash that fires the airbag and renders the car impossible to drive due to suspension misalignment is obviously a different situation but a minor fault that renders the car immobile is not. There needs to be a “get me home” setting or condition.
Needing to replace an ECU due to one response is unacceptable and something needs to be disabled so that can’t happen. If it is a requirement we may all soon end up with a vehicle that needs an ECU that can’t be reprogrammed!

Please clarify the position.

The need to replace the airbag ECU following deployment of the airbags and pretensioners doesnt seem too extreme as a job following an impact. Lots of 2nd hand ones about and probably new old stock too which wouldnt break the bank. Certainly no more hassle to change than say having to unbolt the seats to replace the pretensioners. A pretty quick and simple job.
If someone really wanted to quickly re engineer the dynamics of the SRS shock sensor to reduce the likelihood of it triggering from a minor impact they could always look at mounting it on a rubber buffer rather than having it directly bolted to the metalwork. The next stop along that path to guaranteeing never to have to replace a deployed airbag or SRS ECU could be for them to disconnect the SRS system entirely and use a timer for the SRS warning light for the MOT. IMHO that  could be a false economy though.

Are you perhaps misreading references here to the airbag ECU as meaning the car's main ECU ? The main ECU wouldnt need to be replaced if the airbags went off.
 

Delbourt wrote:

Roverlike in an earlier post you wrote the following 
“If light vanished after restart then SRS ECU did not record impact. If SRS ECU fired any of airbags or pretensioners it would be written within SRS ECU and light would stay on to remeber to replace ECU as well.”

From that I understood that a spurious fault with one of the sensors such as pre-tensioner or the under seat coupling could initiate a SRS situation where the air bag was “fired”. 
I also then thought that you were saying that if an SRS fault was initiated or that the air bag had fired that the fault could not be cleared from the ECU and/or the ECU might prohibit the car from being driven and that is something that would not be acceptable.
Either there must be a means to override that or a means to easily re set it. 
A serious crash that fires the airbag and renders the car impossible to drive due to suspension misalignment is obviously a different situation but a minor fault that renders the car immobile is not. There needs to be a “get me home” setting or condition.
Needing to replace an ECU due to one response is unacceptable and something needs to be disabled so that can’t happen. If it is a requirement we may all soon end up with a vehicle that needs an ECU that can’t be reprogrammed!

Please clarify the position.

All the time I am speaking about SRS/airnag ECU. I never mentioned engine/main ECU.

I never heard of SRS/airbag ECU firing airbag or pretensioners for just a small impact or rather.bumpy road.

If airbags/pretensioners are fired that kind of impact will most likely render your car undriveable.

If you need to replace SRS/airbag ECU because you have light on, and you just bought the car, you need to ask yourself if car suffered some heavy impact which is coveeed with repair.