even though you don't have a passanger airbag you may have the loom which needs to be plugged into something.

I'd disconnect your battery and then follow all the yellow looms to make sure they're all plugged in correctly. SRS plugs usually have to push in and then theres a latch you need to pull as well.

Just make sure all your fuses are good as well. You may have a hair line crack in one or something weird which is still making a connection but only slightly.

Also check any grounds that you can find, make sure they're secure and not rusty.

I just had to reset my SRS light after my alarm installer decided to unplug some looms while he was under there. *shakes head*

Good luck mate.