Your '99 is OBD2 compliant. I've read that jumpering the diag connector doesn't work, so I'm not sure if that code 21 is valid. It would be best to read the codes with an OBD2 reader. Simple ones are cheap these days; about $10-$20 for a basic one. Or most auto parts stores will read 'em for you for free.Yes the bulb works. Actually checked the codes using jumper wire in diagnostics connector and got the 21 = oxygen sensor. Probably the light would appear after running longer without the sensor. I still wonder is it normal that I can't feel any difference with and without oxygen sensor?