Volvo: check engine light, oxygen sensor, negative cable

Question

Hello Ray, my 850 Glt's check engine light came on today and as soon as the light was on the engine stopped.then I started the engine again the car stopped the same way again. then the third time I waited a while and started the engine the engine started and I drove back to home with the check engine light on, the car didnt stop again, felt like the car lost some power, do these cars have a limp mode? after I came back to home, I plugged the negative cable of the battery waited 2 hrs and re plugged it.. the car started normally without the check engine light. now what I want to ask you is,last week I bought 97 octane unleaded fuel for the car and felt like the performance was better, after the low fuel level light came on I bought 95 octane unleaded, this car was driven by 95 octane unleaded fuel by me and the previous owner since it was new do you think 97 octane caused the check engine light to blink? or there might be other causes like the oxygen sensor? should I keep using 95, or 97 or 98 is ok for this car? one last question where is the trans front pump seal is located on this car?

thanks,

Answer
Mete,
The car was designed to run on low octane fuel. The control unit is designed to adjust for different fuels, or even poor fuel. Use the fuel that gives you the mileage and performance you like.
Front pump seal is front of the Trans where it meets the engine. Trans needs to come out to replace it. If the Trans is pulled also replace the rear main engine seal.