when I was changing the plugs in my car today the ratchet hit the O2 sensor and it sparked....the switch was off, why did this happen?

 

If you had a power source on one end of it touched metal it can spark. I did this with my starter and alternator. Kinda scary sometimes.

 

You might have damaged the sensor. There's a 12v wire going to the heating element in the 02 sensor. Maybe you shorted that wire to the housing of the 02 or something? but this wire should only go hot when the ignition is on... so i'm just going to say your car is possessed.

 

Thats what I was afraid of......I feel that the car has been running lean but I have no proof of this other than the plugs look pretty light and this same sparking thing just happened on fri too

 

In your previous post about the "sparking", you thought it was the knock sensor that sparked when you hit it with the ratchet. There is no power to the knock sensor circuit unless the key is on, and its only 5V from the PCM. Now you have an O2 sensor sparking. Again, that circuit (the 12V heater, mentioned above) is only "hot" when the ignition is on. And, the wires and connectors are fully insulated, preventing you from shorting to the + side of the voltage. You might want to take a volt meter, and with the key in the "off" position, probe those sensor housings and others to make sure they are not somehow receiving +12V at the metal housing.

 

yea sorry I didn't get to see wear it was sparking from last week, but this week I did. It was the O2 sensor not the knock sensor....my ratchet hit the O2 sensor when I was removing the plug and it sparked. The key was off....I'll get a meter and get under it and check to see what its doing....

 

Sounds like you've got 12v running through your exhaust...