I recently purchased a 2004 V70 and see that the SRS air bags are due for service. What exactly is involved? A software scan and/or replace parts? The system light is functioning properly at this time. Thanks, Doug

Negative, the SRS system has detected a fault and you need to have the system scanned and the fault repaired. There is NO periodic service for the SRS, it either works or doesn't.
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My back feels better when I sit in a Volvo seat

There is no fault warning or display alert at this time. The service decal on the rear left door sill indicates that it is time for scheduled 10 year service by the dealer.
If you say the system either works or doesn't what would they service?

There is nothing to 'service' in the entire SRS system. The decal you see was written by lawyers to cover their butts. But, the NHTSA requires that SRS systems last for the life of the vehicle, regardless of time and miles.

Obviously, the system cannot be tested. Once the SRS module gets excited and causes an air bag to explode, the SRS module has to be replaced.
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My back feels better when I sit in a Volvo seat

NOT true. it is true that SOME SRS modules cannot be rest after a crash but volvo's Can with the Dice, i have done 3 w air bag deployments, there is the option to to 'crash report reset'

I stand corrected! Thank you.
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My back feels better when I sit in a Volvo seat

I was wondering exactly the same thing when I purchased my 2 2004 V70's.

Nice to know the lawyers are involved (I always get a warm fuzzy feeling...NOT) and there is nothing required of me until the system sees a fault.

cheers