code 13 on my car

[91chevyluminaeuro]

I checked teh codes on my car, i got 13,23,and 33. i pluged the sensor back into my intake and then cleared the codes, ran it today and re-checked the codes i still got code 13, o2 sensor, ive got on but i dont know where its located.... can anyone point me in the right direction? ive got a 91 chevy lumina euro with the 3.1.

[5speedz34]

The O2 sensor is located behind the rear exhaust manifold, on the downpipe. You'll have to rock the motor forward to get to it. I would recommend getting a AC Delco O2 before anything else.