Well, I thought I had fixed my SRS, but over the last month or so it has been coming on more and more again, to the point it was almost on all the time.
I have suspected the drivers side pretensioner since it used to come on when cornering hard, or lately, just when I knocked the seatbelt clip.
Since I had 3 different warning lights on yesterday, I vowed to sort them. MIL eliminator sorted one (I just had to reset the MIL), one was caused by the remap on the rolling road (apparently it confuses the hell out of the ABS system when the back wheels are going round and the fronts aren't) which reset itself after a short drive. So that just left the SRS.
I bought a second hand pretensioner but it had the wrong plug on it. Mine had a yellow plug and the new one had a red plug. The original belt clip had always been twisted as well.
So I decided I wanted the new clip, with the old cable.
WARNING: ALL OF THE MANUALS AND A WARNING LABEL ON THE PRETENSIONER WARN YOU NOT TO CARRY OUT ANY WORK ON THEM. THEY CONTAIN EXPLOSIVES.
If you do follow any of this it is at your own risk.
use a multimeter on the pretensioner or airbag system as they generate voltages and this could cause it to deploy.
I am stupid/brave/inquisitive (Please delete as appropriate).
For those of you that are interested, this is how the pretensioner works.
To remove the unit you must diconnect it electrically (The book says you should disconnect the battery and allow the system to discharge). Definitely DO NOT disconnect the unit when the ignition is switched on.
You have to remove the seat for best access (4 torx bolts. one at each corner). Disconnect the plug under the seat. You don't have to fully remove the seat, but I found it easier.
Remove the Torx bolt holding the pretensioner to the seat and it looks like this.
Notice the clip twisted through almost 90 degrees.
If you do work on the unit, never cover the end of the cartridge, never point it at any part of your body, never hold it by the cable etc. If it goes off it will go off like a shotgun cartidge and all moving parts will operate in milliseconds (Ouch).
I also wore safety glasses and ear defenders.
Slide back the rubber outer to reveal the plug.
The plug simply pulls out with a bit of force. This leaves the nasty bit so that you can put it out of the reach of children and small furry animals.
I would love to know exactly what is in there. I expect it is just an explosive cartridge and a detonator.
This leaves the cable and connectors to work with.
I found some evidence that the cable had been crushed somehow, which is never good.
Also, after taking the cover off the plug I found my least favourite connectors, the ones that you push the cable into and they cut into the wire creating a connection. These are renowned for working loose and causing bad connections.
So I removed the cable (Metal cable restraint clips in/out of the casing) and cut it back past the damage. The metal cable clamps are crimped onto the cable and have to be removed, widened and fitted back onto the cable where it can be crimped back on with a pair of pliers. The newly cut and stripped ends are now placed back in the plug and the cables pushed into the metal cutters to create a new contact.
I checked the connection out with a multimeter (the explosive bit isn't attached at this point). Put the cover back on and reassembled the pretensioner with the new clip. Fitted it back on the seat and fitted the seat.
I have been out for a drive and so far the SRS light hasn't come back on. Only time will tell.
I suspect the push in connections rather than the crush damage, but I fixed both so hopefully that will be that.
If anyone knows the purpose of the inductive coil, or how the system works as a whole, please let me know.