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SRS light is on, and the seat connectors look fine!

2487 Views 32 Replies 14 Participants Last post by  SilverTF, 
Jimmy_MGF
Hey all, I've got the MOT coming up so tried to the standard SRS fix (disconnect/reconnect both seat connectors a couple of times) but this time no luck.

Any suggestions on how I can diagnose where the problem is coming from, or some seasoned advice to point me in the right direction?

I'm also thinking of getting one of those USB OBD readers (my MGF is late 2001 so I think I can use this) - advice on a cost-effective one which you've successfully used would also be appreciated!
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Jimmy_MGF
No judgement, but the ol' brainbox is ticking now. As mowog73 asked; what size resistor did you use?
My logic is if the SRS system checks itself via resistance, I can go around each seat and rotary coupler trying the resistor on each. When the light goes out, I've found the dodgy component!

It probably is the coupler, but I have a box of resistors in my cupboard so always willing to try a quick and easy test first.
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Jimmy_MGF
I'll have to try the resistor trick for Tuesdays MOT :(
Put in a replacement ebay rotary coupler this morning but still a red light. It could be its from ebay, and it did have a slightly different part number, but it was an MG marked original (picture is the one I took out).

Wish I cleaned the airbag connector as suggested above when I had it off!

Any other suggestions as to what I can try are welcome. SRS fuse, maybe?

Plus side is I know how to pull the steering section apart down to the rotary coupler, and next time I dont need to remove the finicky hooter buttons!

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Jimmy_MGF
It was a youtube job. How were you led astray?
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Jimmy_MGF
Yeah nearly. Sorry; was in a rush whilst waiting for the petrol pump.
I was thinking about breaking out the ol' multimeter when I get home to check the old one.
At least if I confirm it is broken then the one installed has probably gone too and I just got unlucky. if it does work.. well I put it back in but back to square 1 on the issue!
Cheers, will report back after I've had another play
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Jimmy_MGF
Sorted! Closing post on this one.

Got some 1 Ohm resistors to trial-and-error the system. Before ripping out the steering wheel I stuck 1x 1 Ohm resistor in each seat connector, bridging their terminals. Light when out, so by process of elimination I found the driver pre-tensioner is the problem.

This was incredibly easy to diagnose so I'll likely keep a 1 Ohm resistor in the spare bits box (ash tray) in case the SRS light comes on again.

Resistor values - I first used 2x 1 Ohm resistors on each seat connector as I read 2 Ohm is needed. This works, but as they were just twisted together I then tried a single 1 Ohm resistor and it still worked.
Crux of it is: 1 or 2 Ohm resistors work to test the seat SRS system. Tried a 33 Ohm resistor out of curiosity and that didn't work, so clearly low value resistors are needed.
I didn't try a resistor the airbag connector as there was no need to pull it off, but if someone tries let me know. I expect a 1-2 Ohm resistor will probably work too.

Cost me a few hours of trial-and-error, and £20 for a new rotary coupler, but I now have a spare and the knowledge to replace it again in future!

Cheers everyone!
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