My check engine light has been on since I replaced my alternator. I finally got around to reading the code and the code is:

P0174
System to lean (bank 2)

O2 Circuit No Activity Detected
(Bank 2, Sensor 1)



Do you think is as simple as just replacing the O2 sensor or is it possibly something else was shorted out when the old Alternator shorted?

How do I know which O2 sensor I need to replace? (IE which one is Bank 2, Sensor 1?) Can someone point me to an engine diagram of where it is located?

first thing to do is erase the fault and see if it returns.as for which sensor it is,bank2 I believe is the right side as you look into the engine bay.sensor 1 is the first sensor in the exhaust system.easiest way to find them is follow the exhaust pipe from the manifold downwards.before you replace any though I would confirm which it is by clearing the codes,unplugging the sensor you think it is and restarting.the unplugged sensor will trip a fault code which will identify which sensor it is.it is a slower process than looking in a book but it will at least make sure you do not change a good sensor.I find this method handy as some of the cars I have worked on have had up to 5 oxygen sensors.good hunting

also as an ofterthought-is there any chance you may have hit/broke or unplugged the sensor when changing the alternator???

It certainly is possible something is hit broke or unplugged, who knows. I looked and it appeared everything was plugged in. But I could only see 2 O2 sensors. I will follow the pipe down and see if I find the other 2 as well.

As far as resetting the code. I first stopped by the autoparts store a week or so ago and read the code. I reset the code and went inside to buy an O2 sensor. This is when I learned there are 4 sensors. They told me I needed to get the code number and find out which sensor it was. But I had reset the check engine code so we were not able to get the code then. It took about 20 miles or so before the light came back on, so this morning I stopped again and wrote down everything. So that is where I am at so far.

If I try and reset the code and unplug one of the sensors, will it trigger the check engine light immediately? Or do I have to drive it for a while first?
Also if I unplug the wrong one will it give me codes for both of them?