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I was driving through the paring lot at work today, and for no apparent reason, having not beat on it or ran it hard, the cel came on and the car died.. When I tried to restart it, the fuel pump relay made a wierd screeching sound the way it did when I got bad basemaps before and the car wouldn't start.. Then I tried a couple more time, no screeching, and I started but still with a cel.. So I jumped the connector and got no flashy flashy, so I unplugged the ecu and plugged it back in, still have a cel but car still starts and revs.. I don want to drive It home even though it's only 3 miles because I don't know what the cel is for

how do I check the cel?
Any idea why could have caused this?
Off topic, but does Crome use the O2 sensor? because it drives ok, doesn't smell like too much gas (suprising because dp ends under oil pan), but my af ratio gauge is just stuck on fully rich..