Le voyant service s'allume au bout d'une certaine période ou d'un certain nombre de kilomètres qui correspond à l'écart entre chaque vidange (genre 15.000km sur le 5cyl.)
Il est là dans le but de rappeler au conducteur l'entretien à faire sur sa volvo!
Mais parfois, les concessions oublient de le supprimer, d'autres font eux-mêmes l'entretien courant et n'ont donc pas la valise pour le supprimer!
Voilà donc les manipulations à faire!
Attention, le forum ne peut en aucun cas être tenu responsable en cas de problème dus à cette manipulation(enfin moi je le fais sur la 854 de 94 et la V70 de 00 et aucun problème

)
Reset Volvo 850 XC70 S70 V70 C70 S80 Service Light
By Matt
850 (1993-1995)
There are two diagnostic units(it says A and B on the cover) located adjacent to washer reservoir under the hood.
1. Turn on the ignition and open the module A and insert the flylead into socket 7.
2. Press the button on the diagnostic unit 4 times, briefly but firmly.
Then the LED illuminates and stays illuminated, and the system is ready to accept manual code input. A code number for resetting the service reminder light is 1-5-1.
3. To do this, press the test button once and release it. And LED illuminates again.
4. Then press 5 times and wait for the LED to illuminate.
5. Press the button once and LED should flashes several times in succession and the reminder should have been reset.
6. Switch off the ignition and replace the flylead in its holder and close the cover.
850 (1996-1997) and S70 and V70 (1998)
You need an OBDII tool that resets Volvo service light codes. See this service light reset forum thread for more. They run about $100 to 200 -- or -- take it in to the dealer or independent Volvo mechanic and have them do it. Call to see if they charge for this first. Note: I've read reports of people having success with having the local Shucks/Pep Boys/Checker auto parts store do it.
S70 and V70 and C70 and XC70
1. Press and hold odometer reset button.
2. Turn ignition switch to Run.
3. After SRL flashes, release odometer reset button.
4. Confirm by turning your Volvo off, then on again.
S80
1. Turn ignition switch to position I.
2. Press and hold "day counter reset button".
3. Turn ignition to position II.
4. Continue holding day counter for about 10 seconds.
5. While SRL flashes, release day counter button.
6. Should hear "beep-beep" to confirm command accepted.
S40 and V40 (1999+)
1. Hold down the odometer button
2. Turn the ignition so all the lights come on
3. Keep holding the odometer down for 30 secs or until the service light starts flashing
4. Release the odometer button while service light flashing
5. Turn off and on again to check
Source :
http://www.matthewsvolvosite.com/reset.php