ABS light on is most likely the ABS control module. The dealer will want $600 or more for it plus labor. Victor Rocha who is a member here repairs many of ours (mine too) and charges $150 including shipping, plus gives you directions on how to get it off and back on. The coolant level might be low or the level sensor is bad or disconnected. Basically, all total about $200 to repair all if you do it yourself. If this is all that's wrong with the car, don't let these 2 things deter you. '97 is the best year for the 850. Also, just to let you know, the ABS module eventually dies in all of these cars, so if it wasn't dead now, it will be most likely during the life of the car.
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1998 S70 T5 Emarald Green Metallic (125K), 2004 V70 2.5T Ruby Red (45K), Previous Owner of Black '94 850 Turbo Wagon (Sold at 140K and miss her). My cars have been running so well lately they've got me worried.