1995 Volvo 850 Volvo Maintenance Reminder Light Reset Procedures

The Service Reminder Indicator (SRI) is triggered at the appropriate interval since last service. Depending on model, this is based on accumulated mileage, calendar time, or hours of engine operation. Once triggered, the SRI comes on each time the engine is started. The light goes out after approximately two minutes except on 850 Base variant (without trip computer). After service is performed and the SRI counter reset, the SRI will not light again until shortly before next service is due.
Service reminder reset knob is located on front of instrument cluster to left of trip odometer reset knob underneath a rubber grommet. To reset, remove the rubber grommet and use a small screwdriver to depress knob. connector (DLC) A. Depress button four times, shortly but distinctly. You have now entered test mode 4. When LED emits steady glow, the system is read to accept code. Enter first digit while LED is still lit (1). Wait until LED glows steadily to enter second digit (5). Repeat procedure for third digit (1). Control module confirms operation by LED giving a couple of rapid flashes. Zeroing is completed and SRI turns off.

Source