All first generation Volvo S80 should get the chassis code "TS".
It includes all 1998 - 2005 models:
http://imcdb.org/vehicles.php?resultsStyle=asImages&yearFrom=&yearTo=2005&makeMatch=- 2&make=Volvo&modelMatch=1&model=S80&modelInclModel=on&modelInclChassis=on&mk=&origin=- &madein=&madefor=&role=

And also these two 2006 models:
http://imcdb.org/vehicle_548262-Volvo-S80-2006.html
http://imcdb.org/vehicle_890280-Volvo-S80-2006.html

Furtheremore, there are currently some 1st gen. S80 without year, which should get the correct year and also the [TS] chassis code.

These should be set as 1998:
http://imcdb.org/vehicle_22309-Volvo-S80.html
http://imcdb.org/vehicle_28379-Volvo-S80.html
http://imcdb.org/vehicle_33266-Volvo-S80.html
http://imcdb.org/vehicle_38920-Volvo-S80.html
http://imcdb.org/vehicle_86128-Volvo-S80.html
http://imcdb.org/vehicle_120605-Volvo-S80.html
http://imcdb.org/vehicle_125578-Volvo-S80.html
http://imcdb.org/vehicle_154879-Volvo-S80.html
http://imcdb.org/vehicle_159813-Volvo-S80.html
http://imcdb.org/vehicle_181168-Volvo-S80.html
http://imcdb.org/vehicle_201695-Volvo-S80.html
http://imcdb.org/vehicle_206135-Volvo-S80.html
http://imcdb.org/vehicle_128561-Volvo-S80.html
http://imcdb.org/vehicle_194477-Volvo-S80.html
http://imcdb.org/vehicle_198603-Volvo-S80.html
http://imcdb.org/vehicle_53822-Volvo-S80.html
http://imcdb.org/vehicle_81882-Volvo-S80.html
http://imcdb.org/vehicle_206711-Volvo-S80.html
http://imcdb.org/vehicle_225119-Volvo-S80.html
http://imcdb.org/vehicle_238069-Volvo-S80.html
http://imcdb.org/vehicle_248367-Volvo-S80.html
http://imcdb.org/vehicle_250704-Volvo-S80.html
http://imcdb.org/vehicle_265576-Volvo-S80.html
http://imcdb.org/vehicle_265615-Volvo-S80.html
http://imcdb.org/vehicle_269631-Volvo-S80.html
http://imcdb.org/vehicle_273198-Volvo-S80.html
http://imcdb.org/vehicle_310033-Volvo-S80.html
http://imcdb.org/vehicle_381499-Volvo-S80.html
http://imcdb.org/vehicle_384315-Volvo-S80.html
http://imcdb.org/vehicle_423953-Volvo-S80.html
http://imcdb.org/vehicle_475282-Volvo-S80.html
http://imcdb.org/vehicle_499198-Volvo-S80.html
http://imcdb.org/vehicle_504531-Volvo-S80.html
http://imcdb.org/vehicle_551553-Volvo-S80.html
http://imcdb.org/vehicle_554992-Volvo-S80.html
http://imcdb.org/vehicle_564598-Volvo-S80.html
http://imcdb.org/vehicle_569712-Volvo-S80.html
http://imcdb.org/vehicle_638743-Volvo-S80.html
http://imcdb.org/vehicle_649956-Volvo-S80.html
http://imcdb.org/vehicle_722065-Volvo-S80.html
http://imcdb.org/vehicle_729086-Volvo-S80.html
http://imcdb.org/vehicle_774966-Volvo-S80.html
http://imcdb.org/vehicle_896086-Volvo-S80.html
http://imcdb.org/vehicle_921497-Volvo-S80.html
http://imcdb.org/vehicle_928967-Volvo-S80.html
http://imcdb.org/vehicle_944989-Volvo-S80.html
http://imcdb.org/vehicle_946568-Volvo-S80.html

These should be set as 2004:
http://imcdb.org/vehicle_7706-Volvo-S80.html
http://imcdb.org/vehicle_164140-Volvo-S80.html
http://imcdb.org/vehicle_197915-Volvo-S80.html
http://imcdb.org/vehicle_100271-Volvo-S80.html
http://imcdb.org/vehicle_125367-Volvo-S80.html
http://imcdb.org/vehicle_184056-Volvo-S80.html
http://imcdb.org/vehicle_12333-Volvo-S80.html
http://imcdb.org/vehicle_36170-Volvo-S80.html
http://imcdb.org/vehicle_212996-Volvo-S80.html
http://imcdb.org/vehicle_233187-Volvo-S80.html
http://imcdb.org/vehicle_237252-Volvo-S80.html
http://imcdb.org/vehicle_245250-Volvo-S80.html
http://imcdb.org/vehicle_316126-Volvo-S80.html
http://imcdb.org/vehicle_353880-Volvo-S80.html
http://imcdb.org/vehicle_393273-Volvo-S80.html
http://imcdb.org/vehicle_423343-Volvo-S80.html
http://imcdb.org/vehicle_484414-Volvo-S80.html
http://imcdb.org/vehicle_643235-Volvo-S80.html
http://imcdb.org/vehicle_645015-Volvo-S80.html
http://imcdb.org/vehicle_941999-Volvo-S80.html

MY unknown, but also [TS]
http://imcdb.org/vehicle_95968-Volvo-S80.html
http://imcdb.org/vehicle_143583-Volvo-S80.html
http://imcdb.org/vehicle_171095-Volvo-S80.html
http://imcdb.org/vehicle_184022-Volvo-S80.html
http://imcdb.org/vehicle_202048-Volvo-S80.html
http://imcdb.org/vehicle_36170-Volvo-S80.html
http://imcdb.org/vehicle_222688-Volvo-S80.html
http://imcdb.org/vehicle_230131-Volvo-S80.html
http://imcdb.org/vehicle_231641-Volvo-S80.html
http://imcdb.org/vehicle_370947-Volvo-S80.html
http://imcdb.org/vehicle_372973-Volvo-S80.html
http://imcdb.org/vehicle_374450-Volvo-S80.html
http://imcdb.org/vehicle_476506-Volvo-S80.html
http://imcdb.org/vehicle_486646-Volvo-S80.html
http://imcdb.org/vehicle_504543-Volvo-S80.html
http://imcdb.org/vehicle_653824-Volvo-S80.html
http://imcdb.org/vehicle_800439-Volvo-S80.html
http://imcdb.org/vehicle_836764-Volvo-S80.html
http://imcdb.org/vehicle_838283-Volvo-S80.html
http://imcdb.org/vehicle_860806-Volvo-S80.html
http://imcdb.org/vehicle_878670-Volvo-S80.html
http://imcdb.org/vehicle_914241-Volvo-S80.html
http://imcdb.org/vehicle_935342-Volvo-S80.html
http://imcdb.org/vehicle_958445-Volvo-S80.html
http://imcdb.org/vehicle_960499-Volvo-S80.html