How to Jump Start a Volvo S90

1. Put the ignition in mode 0 and check that the auxiliary battery is 12 volts.
2. If the helper battery is in another vehicle, switch that engine off and keep the vehicles from touching.
3. Clamp the red cable to the auxiliary battery's positive (+) terminal (1).
4. Fold back the cover and clamp the other red end to your vehicle's positive (+) jump start terminal (2).
5. Clamp the black cable to the auxiliary battery's negative (-) terminal (3), then the other end to your negative (-) ground point (4).
6. Check the cables are firmly attached, then run the assisting vehicle's engine at about 1500 rpm for a few minutes.
7. Start the engine of the vehicle with the dead battery without touching the cable connections.
8. Remove the cables in reverse order, black cables first and then red cables.

• Do not let black clamps touch either vehicle's positive jump start terminals or the red cable clamps.
• Do not connect the jumper cable to the fuel system or moving parts; batteries give off flammable hydrogen gas.
• Do not tow the vehicle to start the engine; use an auxiliary battery.

Source: 2018 Volvo S90 owner's manual, PDF pages 435, 436. Steps are summarized in our own words (AI-assisted, checked against the cited pages 2026-10-18). Other model years can differ; your manual has the final word.