hi im a vw guy but my father in law needs help with his saab. its throwing a p0340 code and wont run. it turns over but wont run. this problem came out of nowhere and one day he walked outside and the car wouldnt run. i was reading around and some people were saying its the sensor but some were saying it was the spark plugs. should i just try the spark plugs first before ordering the sensor or would the spark plugs not cause this severe of an issue and just get the sensor now?

edit: its a 98 900 se turbo but i couldnt find that forum in here so i just posted here. dont make fun of me or make me cry please.