i had this problem and searched the net for an answer , i couldnt find one and after a few pm,s sent to other who hadnt found a solution i decided to sort it myself.
here is the solution , its a simple ecu configeration mismatch, to confirm you may go into the airbag ecu programming in diag software of your choice , it will tell you that the airbag module is already programmed and locked ignore this and look at the values programmed, you will see seat occupancy not configured . basically the airbag ecu isnt expecting any resistance on the wire to the PASSENGER SIDE seat occupancy sensor. the old interior didnt have seat occupancy so all was correct, how ever your new seat HAS got seat occupancy so the airbag ecu has sensed this due to the resistance being measured on the signal wire.
this can also happen the oposite way aroud where the airbag ecu has got the seat occupancy set to PRESENT but your new seats dont have the seat occupancy sensor. both are easily solved.
1st senario is most commonley expected.
2 easy fixes
remove earth terminal from the battery wait 30 minutes
. 1st you can simply cut pin 9 on the connector under the passenger seat, or 2nd you can unplug the single plug from the multy plug that contains pin 9. i did the later of the 2 as its easier should i ever revert back to interior that was in it.
either way reconnect the multy plug and reconect the battery, turn on ignition and the airbag light will go out thers no need for any programming of any sort or fault code erasing.
just to let you know 1st time i turned on ignition after i had done above i was stood outside of car just in case of any airbag firing off, not that it was expected i just thought it made sense!!!
2nd scenario is no seat occupany detector and the airbag is looking for it
2 thing to do 1st is a cowboy fix which i wouldnt do and that is simpley to add a 4 ohm resistor to pin 9 of the multy plug so you are kidding the airbag ecu, drawback is SAFETY FOR PASSENGERS as no airbag will be deployed if it was ever needed, thats why i wont tell you exactly how to do it , but theres enough info to get you started.
2nd and the proper way is just as simple but will cost a few quid and will result in safety for your passengers BUT IM NOT SURE AS I HAVNT LOOKED INTO IT is for baby seats, so if you intend a baby seat for front passenger i suggest you make more detailed enquires but im sure it will lead into buying a new airbag ecu for a quite a few hundred pounds,
all wiring is inplace upto the multyplug under the seat as old interior requires it, simply buy a seat occupancy sensor or grab one from a goosed breaker car (in the foam where you bum sits on ) and plug it in on pin 9 connector and fit the mat in the foam , this way your airbags should be fully operative with no kidding and work just the way there meant to for passengers.
heres a pic of the block uner the seat with pin 9 circled in red.
please do note this is from my own finding and please use it as that, i didnt deisighhn the electronic system in vauxhalls just tried and tested above scenarios.